Имя плагина	azurecurve BBCode
Type of Vulnerability	Authenticated Stored XSS
CVE Number	CVE-2025-8398
Срочность	Низкий
CVE Publish Date	2025-09-11
Source URL	CVE-2025-8398

Urgent: CVE-2025-8398 — Authenticated (Contributor+) Stored XSS in azurecurve BBCode (<= 2.0.4) and how WP‑Firewall protects you

Опубликовано: 11 September 2025
CVE: CVE-2025-8398
Affected: azurecurve BBCode plugin ≤ 2.0.4
Severity (reported): CVSS 6.5 — stored Cross‑Site Scripting (XSS) via the url shortcode
Required privilege to exploit: Contributor

As a WordPress security practitioner working on WP‑Firewall, I want to walk you through what this vulnerability means, how an attacker could exploit it, how to detect if your site is affected, and — most importantly — practical mitigation steps you can take immediately to protect your sites. I’ll also show developer‑level guidance to permanently fix the issue in the plugin code and suggest WAF signatures and virtual‑patching approaches that we apply to block attacks before an official vendor patch lands.

This is written in plain language for site owners and with technical depth for developers and security teams. If you manage or host WordPress sites, read this start‑to‑finish and take the remediation actions described below.

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Executive summary — what happened and why you should care

• A stored XSS vulnerability (CVE‑2025‑8398) exists in azurecurve BBCode plugin versions up to and including 2.0.4.
• A user with Contributor privileges (or higher) can create content that includes a malicious payload constructed via the plugin’s [url] shortcode. That malicious content is stored in the database and executed later when the page/post is rendered in a browser (for admins, editors or site visitors depending on visibility).
• Because the payload is stored, it can execute whenever the affected content is viewed. This gives an attacker an opportunity to execute javascript in the context of your site — potentially stealing cookies/tokens, performing actions as an admin when an admin views the content, or delivering redirects/malicious scripts to site visitors.
• There is no official patch available at the time of this writing. That means mitigation needs to be applied on your site immediately — either by removing/disabling the plugin, sanitizing stored content, restricting user privileges, or applying virtual patching via a WAF.

Why it’s important: Contributor accounts are common on multi-author sites, educational blogs, and user‑generated content systems. If you allow people to create content but not publish, they can still lodge malicious payloads that execute later. Stored XSS is one of the most damaging XSS types because the malicious code persists on the server.

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How the vulnerability works — technical explanation

The plugin exposes a [url] shortcode that converts BBCode-like syntax into HTML anchor tags when posts are rendered. The vulnerable behavior boils down to two mistakes:

1. The shortcode accepts user-supplied attributes/content and outputs them to the page without adequate validation/sanitization and without restricting URL schemes. This allows input like javascript: or markup containing onerror handlers when attributes are inserted into an HTML context without proper escaping.
2. The output encoding is not enforced for the proper HTML context (attribute vs. element content), or the plugin uses unsafe string concatenation to build anchors.

Typical vulnerable shortcode example (conceptual):

[url="javascript:"]Click me[/url]

When this gets translated to HTML incorrectly, it can produce an anchor that executes javascript when clicked or even when rendered if injected into attributes such as onmouseover или onerror on an image tag.

Stored XSS risk vectors:

• A malicious Contributor creates a new post or a comment containing the malicious shortcode. Even if it is stored as pending, the payload can execute when an admin/editor previews the post, or when another user views it (if the site publishes items automatically).
• The plugin might also process shortcodes in user profile fields, widgets, or other content areas.

In short, contributor‑level accounts can place content that will later be rendered by a page viewed by higher‑privileged users — this is why stored XSS is significantly dangerous.

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Realistic attack scenarios

• Scenario A — Admin preview: A contributor writes a post using the malicious [url] shortcode and asks for review. When an editor/admin opens the preview (or the editing screen that displays the rendered post), the stored script executes in the admin’s browser session. The script can make authenticated requests, create an admin user, change options, or exfiltrate cookies and nonces.
• Scenario B — Published content on a public site: The malicious shortcode is used in a post that is auto-published or published by someone who doesn’t notice the payload. Site visitors receive the malicious script and can be redirected to phishing pages, have ads injected, or have their sessions compromised.
• Scenario C — Widget/profile abuse: If the plugin processes shortcodes in widgets, sidebars, or user profile outputs, the attacker can place the payload in areas visible across many pages, magnifying impact.

Remember: even if contributors cannot publish, their content can still cause damage if previewed by an admin or if another privileged user publishes it.

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How to check whether you’re affected (detection)

1. Identify plugin versions:
   • Go to your WordPress Admin → Plugins and verify the installed version of azurecurve BBCode. If it is ≤ 2.0.4, your site is in scope.
2. Search for suspicious shortcodes in the database:
   • Use a search in the wp_posts и wp_postmeta tables for raw occurrences of [url (case-insensitive).
   • Example SQL (run read-only queries or via your host control panel / phpMyAdmin):
     SELECT ID, post_title, post_author FROM wp_posts WHERE post_content LIKE '%[url%';
   • Also search comments, user meta, widget options, and other stored content tables:
     SELECT * FROM wp_comments WHERE comment_content LIKE '%[url%';
SELECT * FROM wp_usermeta WHERE meta_value LIKE '%[url%';
3. Look for encoded/obfuscated payloads:
   • Attackers often encode strings (e.g., javascript: encoded as javascript:) — search for javascript: patterns and common on* handlers (onerror=, onload=) in content.
4. Scan for known indicators:
   • Strings like javascript:, data:text/html, <script, или onerror= inside saved content are immediate red flags.
5. Check access logs and admin activity:
   • If an exploitation is suspected, check webserver logs for POSTs creating suspect posts and check WordPress user activity for unusual previews or logins at the time the malicious post was saved.
6. Run a targeted malware scan:
   • Use your security tools to scan posts and database fields for inline scripts or suspicious attributes.

If you find matches, treat them as compromised until proven otherwise. Remove or sanitize the content, rotate credentials, and follow the containment steps below.

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Immediate mitigation steps you should take (site owner / admin)

If you host WordPress sites or manage many installations, follow these steps now:

1. Disable or remove the vulnerable plugin:
   • If you do not require azurecurve BBCode, deactivate and delete the plugin immediately. This is the fastest way to stop the shortcode from being processed on the front end.
   • Note: Deleting the plugin typically does not remove content that contains the BBCode; it just stops it from being processed into HTML. So you should still scan and sanitize stored content.
2. Restrict Contributor privileges temporarily:
   • Change user roles: If you have an environment where you can temporarily change Contributors to a safer role (or suspend accounts until a patch is installed), do so. At minimum, review pending posts and new content before publishing.
3. Audit pending posts and new posts:
   • Inspect content posted recently by contributors. Look for [url shortcodes or suspicious strings. Remove or sanitize any suspicious entries.
4. Sanitize the database:
   • Replace or remove malicious payloads in the database. Prefer manual review to automatic replaces, but if mass cleanup is necessary, search and replace suspicious patterns with sanitized versions or plain text.
   • Back up your database before making sweeping changes.
5. Rotate credentials and secrets:
   • If you suspect that an admin account was compromised, rotate passwords and invalidate sessions (Users → All Users → Sessions). Consider rotating API keys and secrets if you integrated other systems.
6. Add or enable WAF / virtual patch:
   • Put in place a Web Application Firewall rule to block exploit traffic patterns (examples below). If you use WP‑Firewall, enable virtual patching for this vulnerability so we block attack vectors even while there’s no upstream patch.
7. Notify and monitor:
   • Let your team and stakeholders know the issue and actions taken. Increase monitoring on logs and WAF alerts for the next 48–72 hours.

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Developer guidance: how to fix the plugin code

If you’re a plugin developer or comfortable editing plugin code, here are secure practices and an example of how to safely handle a url shortcode.

High‑level rules:

• Validate and sanitize input — never trust user input.
• Restrict URL schemes to safe protocols (http, https, mailto, etc.).
• Escape output for the correct context: use esc_attr() for attributes, esc_url() / esc_url_raw() for URLs, and esc_html() for text content.
• Использовать wp_kses() when allowing limited HTML, and supply a policy of allowed elements and attributes.

Example: Safe shortcode handler (conceptual). Replace the plugin’s insecure handler with this sanitized routine.

/**
 * Safe handler for [url="..."]link text[/url]
 */
function wp_firewall_safe_url_shortcode($atts, $content = null) {
    // Normalize attributes
    $atts = shortcode_atts( array(
        'href' => '', // support both [url="..."] and [url href="..."]
    ), $atts, 'url' );

    // Accept a legacy form where the attribute is the key-less value
    if ( empty($atts['href']) && isset($atts[0]) ) {
        $atts['href'] = $atts[0];
    }

    $raw_href = trim( $atts['href'] );

    // Basic normalization: remove surrounding quotes
    $raw_href = trim( $raw_href, "'"" );

    // Only allow safe protocols
    $allowed_protocols = array( 'http', 'https', 'mailto' );
    $parsed = wp_parse_url( $raw_href );
    $scheme = isset( $parsed['scheme'] ) ? strtolower( $parsed['scheme'] ) : '';

    if ( $scheme === '' ) {
        // No scheme: assume https for safety or treat as relative path
        $safe_url = esc_url_raw( $raw_href ); // relative path allowed
    } else {
        if ( ! in_array( $scheme, $allowed_protocols, true ) ) {
            // Disallow dangerous schemes such as javascript:, data:, vbscript:
            return esc_html( $content ?: $raw_href );
        }
        $safe_url = esc_url_raw( $raw_href );
    }

    // Escape for attribute context
    $escaped_url = esc_url( $safe_url );
    $link_text = $content !== null ? wp_kses_post( $content ) : $escaped_url;

    // Build safe anchor
    return '<a href="' . $escaped_url . '" rel="noopener noreferrer">' . esc_html( $link_text ) . '</a>';
}
add_shortcode( 'url', 'wp_firewall_safe_url_shortcode' );

Notes:

• esc_url_raw is used to normalize the URL; esc_url for output; esc_html for link text to avoid HTML injection.
• We explicitly block non‑allowed schemes such as javascript: и data:. That’s critical to prevent XSS via URL schemes.
• We use wp_kses_post() if the content is to allow limited HTML, but prefer plain text for link text.

If you are not comfortable editing code, disable the plugin and contact the plugin maintainer to request a secure release.

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Suggested WAF signatures and virtual patch examples

If your site cannot immediately remove the plugin, apply WAF rules to block common exploit patterns. Below are conceptual rules you can apply in your WAF or virtual patch engine. Adjust according to your platform’s syntax.

1. Block dangerous URL schemes used in shortcode attributes:
   • Pattern to detect javascript: или data: inside shortcode attributes:
     • Regex (conceptual): \[url[^\]]*(?:=|href=)['"][^'"]*(?:javascript:|data:|vbscript:)[^'"]*['"]
   • Action: Block or challenge the request.
2. Block inline event handlers embedded in shortcode parameters:
   • Regex: \[url[^\]]*(?:=|href=)['"][^'"]*(?:onerror|onload|onmouseover|onclick)\s*=\s*[^'"]*['"]
   • Action: Block.
3. Block encoded javascript: strings:
   • Many attackers obfuscate by HTML entity-encoding the scheme. For prevention, detect common encodings:
     • Искать javascript:, javascript:, etc. (use case‑insensitive matching and check for j.*a.*v.*a.*s.*c.*r.*i.*p.*t: pattern).
4. Monitor for shortcode mass creation:
   • Detect POST requests creating posts that contain [url when the author role is Contributor — log and alert.

Example ModSecurity rule (simplified, adapt to your environment):

SecRule REQUEST_BODY "(?i)\[url[^\]]*(?:=|href=)['\"][^'\"]*(?:javascript:|data:|vbscript:)" \
    "id:123456,phase:2,deny,log,msg:'Block possible BBCode url shortcode with dangerous scheme'"

Important: test rules in detection mode first to avoid false positives. Tune whitelists for legitimate use cases.

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How to safely remove dangerous stored payloads

1. Backup first:
   • Export your database before any modifications.
2. Manual inspection is safest:
   • Inspect flagged posts and either edit them to remove the shortcode or change the content type.
3. Sanitization scripts:
   • If you must mass‑clean, use controlled scripts that replace suspect shortcode attributes with safe text. Example (pseudo‑PHP):

$posts = $wpdb->get_results( "SELECT ID, post_content FROM $wpdb->posts WHERE post_content LIKE '%[url%'" );
foreach ( $posts as $p ) {
    $clean = preg_replace( '/\[url[^\]]*(?:=|href=)(["\'])(.*?)(\1)\]/i', '[url_removed]', $p->post_content );
    // Only update if changed
    if ( $clean !== $p->post_content ) {
        $wpdb->update( $wpdb->posts, array( 'post_content' => $clean ), array( 'ID' => $p->ID ) );
    }
}

4. Replace with safe output:
   • Replace malicious anchors with plain text or with sanitized anchors produced by the safe shortcode handler.
5. Re-scan to confirm removal of payloads.

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Post‑incident actions (if you suspect exploitation)

• Immediately isolate the site from inbound traffic if possible (maintenance mode) while investigating.
• Rotate admin accounts and force password resets for users with elevated privileges.
• Check for new administrator accounts, changed themes/plugins, unexpected scheduled tasks, or modified core files.
• Run a full malware scan and consider a professional incident response if sensitive data is likely exposed.
• Restore from a pre‑compromise backup if necessary, but ensure the vulnerability is remediated before bringing the site back up.

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Why CVSS and the reported severity might not tell the whole story

The vulnerability is reported with CVSS 6.5 and labeled “low” in some listings. CVSS is a standardized way to score vulnerabilities, but its numeric severity does not capture contextual specifics like how many sites use the plugin, which user roles are typically available on your site, or how the plugin is used in your environment.

Stored XSS that can be triggered by admin accounts is often more severe in practice because it can lead to full site takeover. Evaluate the risk for your deployment:

• Do you allow contributor accounts? (Yes → higher risk)
• Do editors/admins preview or interact with contributor content in ways that cause the payload to execute? (Yes → higher risk)
• Is the plugin used in widgets or global templates? (Yes → wider exposure)

Treat the vulnerability seriously and err on the side of defense.

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Best practices to prevent similar issues in the future

Для владельцев сайтов:

• Limit privileged roles. Only assign Contributor or higher when necessary and monitor content created by those roles.
• Require moderation for posts by low‑trusted users. Remove automatic publishing by contributors.
• Keep a WAF and automated virtual patch capability enabled to protect against known issues until vendor patches are released.
• Maintain tight change control and backups so you can recover quickly.

For plugin developers:

• Validate and sanitize all user input. Use WordPress sanitization functions consistently.
• Escape output for the context it is used in: attributes vs. HTML content.
• Restrict allowed URL schemes and use white lists.
• Run code reviews with security in mind and include tests for XSS vectors.
• Provide a timely security disclosure process so issues can be reported and patched.

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Example of a mitigation plan (48‑hour checklist)

Day 0 (discovery / publication):

• Inventory: find all sites with azurecurve BBCode ≤ 2.0.4.
• Short‑term mitigation: deactivate plugin where possible. If not possible, enable virtual patch (WAF rule) to block exploit patterns.
• Start database scanning for suspicious [url shortcodes.

Day 1:

• Manual review of flagged content by administrators.
• Remove/sanitize malicious entries.
• Rotate admin credentials and invalidate sessions.
• If evidence of compromise, begin incident response procedures.

Day 2–7:

• Monitor logs for new attempts and WAF events.
• Apply permanent fix when vendor releases a patch or implement developer fix locally.
• Document lessons learned and update deployment and plugin approval processes.

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How WP‑Firewall protects you (virtual patching & monitoring)

At WP‑Firewall we provide managed WAF rules and virtual patching that can block the exploit vector described above the moment a vulnerability is published. Key protections we apply for this class of vulnerability:

• Signature rules to stop dangerous schemes (javascript:, data:) in shortcode attributes and encoded variants.
• Behavior rules to flag and block POSTs that create content containing suspicious patterns when the author role is Contributor.
• Continuous monitoring and alerts when blocked attempts happen, so site owners can investigate whether an exploit was attempted.
• Optionally, automated sanitization suggestions and guidance for administrators to find and remove stored payloads.

Note: virtual patching does not replace a vendor fix; it provides protection while an official patch is developed and tested.

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Developer checklist to produce a long‑term fix

1. Replace any string concatenation used to produce anchor tags with proper escaping (esc_url, esc_attr, esc_html).
2. Restrict URL schemes using wp_allowed_protocols or custom validation.
3. Write unit and integration tests to assert that javascript: и data: are rejected.
4. Document the security model for shortcodes and educate maintainers to avoid parsing HTML with user input.
5. Add a security advisory and release a fixed version, notifying users to update.

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Indicators of compromise (IoC) — things to look for

• Stored content with [url shortcodes containing javascript: или data: schemes.
• Instances of <script> tags or on* event attributes in post_content, comment_content, or user meta.
• Unexpected admin actions soon after content with shortcodes is created (e.g., new admins, changes to theme/plugin files).
• Suspicious outgoing traffic from your site or connections to unknown domains following visits to certain pages.

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Get Immediate Protection with WP‑Firewall’s Free Plan

If you want to protect your WordPress sites while you investigate and remediate, consider starting with WP‑Firewall’s Basic (Free) plan. The free plan includes essential protections that are designed to stop exploit attempts like this one:

• Managed firewall rules and a Web Application Firewall (WAF) to block known and new attack patterns
• Unlimited bandwidth so protections can stay enabled without performance surprises
• Malware scanner to help detect suspicious stored payloads
• Mitigations for OWASP Top 10 risks

You can sign up for the free plan here: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

If you need additional capabilities — automatic malware removal, IP blacklisting/whitelisting, monthly security reports, or automated virtual patching — our Standard and Pro plans are designed to scale depending on your needs.

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Closing thoughts

Stored XSS vulnerabilities like CVE‑2025‑8398 are reminders that even lower‑privilege accounts (Contributor) can be a vector for site compromise when certain plugins process and render user content insecurely. The attack surface is not only core WordPress but also plugins that process BBCode/shortcodes and user input.

Immediate actions you can take: deactivate the vulnerable plugin, sanitize stored content, restrict contributor privileges, rotate credentials, and enable WAF protections (virtual patching) until an official fix is available.

If you manage a large fleet of WordPress sites, make virtual patching and centralized WAF management part of your baseline security practice — they dramatically reduce exposure while you wait for vendor patches and complete remediation.

If you’d like help assessing your sites, configuring virtual patches for this specific vector, or scanning your database for suspicious shortcodes, WP‑Firewall support can assist. Sign up for the free plan to start protecting your site immediately: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

Stay safe and keep plugin inventories and privileges tight — most compromises start with small oversights that are easy to prevent with consistent security hygiene.