Plugin Name	WebP Express
Type of Vulnerability	Sensitive Data Exposure
CVE Number	CVE-2025-11379
Urgency	Low
CVE Publish Date	2025-12-03
Source URL	CVE-2025-11379

Sensitive Data Exposure in WebP Express (<= 0.25.9): What WordPress Site Owners Must Do Now

Published on 2025-12-04 by WP‑Firewall Security Team

Short summary: A recently disclosed vulnerability (CVE-2025-11379) affects the WebP Express WordPress plugin (versions <= 0.25.9). It allows unauthenticated users to access sensitive information that should not be publicly available. This post explains the risk, real-world impact, how to detect abuse, and practical steps you can take immediately — including how our WP‑Firewall protections can shield your site while a permanent fix is rolled out.

TL;DR (If you only read one section)

• Vulnerability: Unauthenticated information disclosure in WebP Express (<= 0.25.9), CVE-2025-11379.
• Risk level: Low-to-moderate (CVSS 5.3) for direct exploitation, but the information leaked can enable follow-on attacks.
• Immediate actions:
  • Remove or deactivate the plugin if you do not need it.
  • If you must keep it, restrict access to plugin endpoints (via WAF, webserver rules or .htaccess) and rotate any secrets that may have been exposed.
  • Enable an application firewall (WAF) with virtual patching rules that block access to the vulnerable endpoint(s).
  • Monitor your logs for suspicious requests to plugin paths and for unusual outbound connections from the server.
• WP‑Firewall customers: We have targeted virtual patching and WAF signatures to block known exploit vectors and protect sites immediately; learn more below or try our free plan.

---

Background: What was disclosed

On 3 December 2025 a security researcher reported an unauthenticated information exposure issue in the WebP Express plugin for WordPress (affecting versions up to and including 0.25.9). The issue has been assigned CVE‑2025‑11379.

In plain terms: an unauthenticated visitor (not logged into WordPress) can access information produced or stored by the plugin that should only be available to administrators or the server itself. That data can include internal file paths, conversion/cache metadata, configuration values, and — depending on deployment — other environment details. While the vulnerability does not directly enable arbitrary code execution on its own, this sort of reconnaissance is frequently used by attackers to plan subsequent attacks (targeted uploads, credential theft, host pivoting, and more).

The vulnerability is classed under OWASP A3 (Sensitive Data Exposure) and Patch Priority/Severity assessments put it in the low-to-medium range — meaning exploitation for direct site takeover is unlikely in most environments — but the downstream risks from leaked information can be material.

---

Why this matters: the real risk from “just data”

It’s tempting to dismiss “information disclosure” vulnerabilities as less severe than remote code execution flaws. Don’t.

• Reconnaissance multiplier: An attacker who can enumerate server paths, config values or plugin internals can craft precise follow‑up attacks — for example, locating writable directories for malicious file upload, discovering backup file names, or identifying third‑party keys and endpoints that can be abused elsewhere.
• Credential compromise: If any API keys, tokens or database connection hints are revealed, the attacker may gain sideways access.
• Social engineering and direct targeting: Knowledge about the technologies and versions you run makes phishing and targeted attacks easier and more convincing.
• Supply-chain and targeted exploitation: Many automated scanners look for information disclosure indicators; once your server matches known assessment criteria it can be added to more aggressive scanning and exploitation lists.

In short: information exposure frequently converts into higher‑impact compromise when combined with other weak points.

---

How the vulnerability typically looks (high-level technical description)

To protect infrastructure, defenders need to understand the mechanics — but we will avoid step‑by‑step exploit instructions.

• A plugin endpoint (publicly reachable) returns or exposes internal data structures or files when invoked by an unauthenticated HTTP request.
• That endpoint may be a REST route, a direct script under the plugin directory, or an AJAX action that does not require authentication checks.
• The data returned can include:
  • File paths or directory listings for plugin cache and conversion folders.
  • Conversion logs or status dumps (which may include server-side error messages).
  • Configuration values (some of which may contain hostnames, URLs, or API endpoints).
• The root cause is typically missing or incorrect permission checks (e.g., assuming a request is safe because it comes from the frontend) or oversharing debugging information in responses.

Because the issue is an information leak rather than code execution, automated scanners will often flag it as medium risk. Attackers, however, use these details like breadcrumbs.

---

What administrators should not do

• Don’t try to “exploit” the vulnerability on other people’s sites — that is illegal and unethical.
• Don’t publicly post exploit code or specific request payloads that trigger the leakage — doing so will accelerate malicious use.
• Don’t assume “low severity” means “ignore” — information leakage can compound with other vulnerabilities.

---

Detection: what to look for in logs and monitoring

You should start by auditing server and application logs for suspicious activity. Look for:

• HTTP requests to plugin-specific paths such as:
  • /wp-content/plugins/webp-express/
  • Any publicly reachable script inside that plugin folder.
• Unusual GET or POST requests that return HTTP 200 with unusually detailed JSON, XML, or HTML containing file paths or server messages.
• Repeated requests from the same remote IP (or small set of IPs) across multiple sites on your hosting provider, especially to plugin endpoints.
• Requests that include scanning-like query strings or suspicious headers and user‑agents.
• Any spikes in failed login attempts after suspected reconnaissance — attackers often follow reconnaissance with credential stuffing or targeted brute force.

Practical log search examples (your log query tool will vary):

• Search for requests containing “webp-express” in the request path.
• Filter responses with length or content-type changes (e.g., JSON responses larger than expected).
• Correlate timestamps with abnormal CPU/IO spikes that could indicate a follow-on exploit attempt.

---

Immediate mitigation steps (quick, practical)

If you manage WordPress sites, take these steps now — prioritize high-traffic and high-value sites first.

1. Inventory and prioritize:
   • Identify all sites that run WebP Express and the plugin version.
   • If you have managed sites, notify site owners and stakeholders.
2. Recommended immediate actions:
   • Deactivate the plugin if it is not required for your site’s operation.
   • Apply webserver-level restrictions to block direct access to the plugin directory or the specific endpoints suspected of leakage:
     • Example (Apache/.htaccess):
       • Deny access to the plugin folder for all requests that are not internal or authenticated.
     • Example (Nginx):
       • Return 403 for requests matching /wp-content/plugins/webp-express/* unless authenticated.
   • If you rely on WebP Express for image conversion, consider temporary alternatives (server-side image conversion tools or other well‑maintained plugins) until the plugin is updated.
3. Rotate and audit secrets:
   • If you believe any API keys, tokens, or credentials may have been exposed, rotate them immediately.
   • Review access logs for unusual activity tied to any third‑party services that might use those keys.
4. Harden file and directory permissions:
   • Ensure the webserver user cannot serve or execute files in unintended directories.
   • Restrict public access to plugin caches, logs and tmp folders.
5. Increase monitoring and alerting:
   • Add log alerts for requests to the plugin paths and for any indicators noted in the Detection section.
   • Monitor for new domains/IPs requesting multiple distinct paths across many of your sites.
6. Consider removal:
   • If the plugin is not core to your business and has no immediate secure replacement, uninstall it until a patched release is available.

---

Web application firewall (WAF) as an immediate safeguard

A properly configured WAF is one of the fastest ways to reduce exposure when a plugin vulnerability is discovered.

How a WAF helps here:

• Blocks unauthenticated requests targeting known vulnerable endpoints.
• Provides virtual patching — i.e., apply a defensive rule that prevents the vulnerability from being reached even if the plugin remains installed.
• Rate-limits or blocks scanning behavior to slow or stop mass exploitation attempts.

Recommended WAF controls for this vulnerability:

• Block or challenge requests to plugin paths (e.g., any request to paths containing /wp-content/plugins/webp-express/ from unauthenticated IPs).
• Deny requests with signs of automated scanning (suspicious user agents, fast request bursts).
• Inspect response content and block requests that trigger disclosure response patterns (e.g., responses containing ‘/wp-content/uploads’ or unusual file path strings).
• Apply virtual patch signatures that specifically target known request patterns used to trigger the information leak.

If you run an application firewall, enable these protections immediately. If you do not have a WAF, apply webserver-level rules (see Immediate mitigations) and consider deploying a managed WAF service to bridge the gap while you patch.

---

WP‑Firewall specific guidance (how we protect your site)

As the team behind WP‑Firewall, our approach to protecting customers in a situation like CVE‑2025‑11379 includes:

• Rapid virtual patch deployment: As soon as the vulnerability is verified, we release WAF signatures that block the exact request patterns used to elicit the information leak — this prevents exploitation even if the plugin stays active.
• Behavioral detection: We detect scanning and reconnaissance patterns and throttle or challenge them before they can consistently harvest information.
• Managed mitigation options: For customers on our paid plans, we offer automatic lock-down configurations (temporary suppression of plugin endpoints) and tailored incident support.
• Security guidance and logging: We surface indicators in our interface so site owners can see blocked attempts, IP addresses involved, and recommended remediation steps.

If you rely on our free plan, you already get essential managed firewall protection, WAF rules, unlimited bandwidth, malware scanning, and mitigation for common OWASP Top 10 risk patterns — these features materially reduce exposure to plug-in information leaks while you plan more permanent fixes.

(See the closing section below for a short paragraph about the free plan and how to get started.)

---

Longer-term fixes and hardening (beyond the emergency window)

Once the immediate emergency is under control, plan for the following:

• Patch management:
  • Track security advisories for the WebP Express plugin and apply the vendor-supplied fix when available.
  • Implement a plugin update policy: test updates in staging, schedule routine updates, and maintain a plugin compatibility checklist.
• Least privilege:
  • Minimize the number of plugins that run sensitive tasks.
  • Ensure sensitive operations (such as cache invalidation or file conversion) require appropriate capability checks in code.
• Disable verbose diagnostics in production:
  • Ensure plugins do not output detailed server-side error messages to unauthenticated requests.
  • Disable debug outputs and logging to publicly accessible endpoints.
• Code review and secure development lifecycle:
  • For plugin authors or in-house developers, adopt automated security scans, threat modeling, and code reviews focused on access control.
• Network segmentation:
  • Limit access to administrative APIs and internal endpoints to specific IP ranges or via authenticated channels.
• Backups and recovery planning:
  • Maintain air-gapped or off-site backups.
  • Regularly test restore procedures to reduce downtime if you must rebuild after an incident.

---

Incident response playbook (concise, actionable)

If you detect abuse or signs of compromise related to this vulnerability:

1. Contain
   • Remove or deactivate the vulnerable plugin.
   • Apply WAF rules and webserver-level restrictions.
   • Block offending IPs and ranges (temporary).
2. Investigate
   • Review access logs for suspicious requests pre-dating mitigation.
   • Check for unexpected file changes, backdoors, or new admin users.
   • Inspect outbound connections from the server and database access logs.
3. Eradicate
   • Remove injected files and restore from a clean backup if necessary.
   • Rotate credentials, API keys and tokens that might have been exposed.
   • Harden file permissions and configuration.
4. Recover
   • Reinstall a clean copy of WordPress and plugins from trusted sources.
   • Re-apply security controls and testing in a staging environment before going live.
5. Post-incident
   • Document the timeline, root cause, and lessons learned.
   • Review monitoring, process and controls to prevent recurrence.

If you need incident support and you are a WP‑Firewall customer, our incident assistance offering can help with triage, log review and containment guidance.

---

Example WAF rule ideas (conceptual)

Below are high-level conceptual rules you can implement in your WAF or webserver. These are defensive patterns — not exploit instructions — and are safe to implement.

• Block unauthenticated access to plugin directories:
  • If request URI contains /wp-content/plugins/webp-express/ and request is not from an authenticated admin session, return 403.
• Rate-limit and challenge scanning behavior:
  • If an IP makes > X requests to distinct plugin paths in Y seconds, challenge with CAPTCHA or temporarily block.
• Block suspicious response patterns:
  • If a response generated by a plugin contains sequences matching internal path patterns (e.g., /var/www/, wp-content/uploads), block the request and log details for investigation.
• Monitor and alert:
  • Generate an alert for any 200 OK responses from plugin endpoints that contain file path strings or debug output.

If you’re using WP‑Firewall, our team crafts and deploys these types of rules centrally so you don’t have to manage the low‑level matching yourself.

---

Frequently asked questions (FAQ)

Q: If the plugin is exposing configuration, do I need to rotate my database password?
A: Rotate any credentials or keys that are plausibly exposed. If you see evidence that a specific secret was leaked (for example, an API endpoint or token present in plugin output), rotate it immediately and audit access logs to confirm no unauthorized use.

Q: Can a WAF fully protect me if I keep the plugin active?
A: A WAF can block exploitation vectors (virtual patching), detect scanning, and slow attackers. However, the only complete fix is to apply vendor patches or remove the vulnerable plugin. Use the WAF as a strong temporary mitigation while you patch.

Q: Is this vulnerability being actively exploited in the wild?
A: At the time of disclosure, automated scanners and some early exploitation attempts are common when such vulnerabilities are announced. Treat your environment defensively — assume scanning is happening and act quickly.

Q: My hosting provider manages my site — do I still need to act?
A: Yes. Confirm with your host whether they have applied protections or blocked the vulnerable paths. Hosts sometimes provide WAF/edge protection, but you should verify and monitor for any access to the endpoints in question.

---

Protect Your WordPress Site — Start with WP‑Firewall Free Plan

Secure, Immediate Protection — Start with WP‑Firewall Free

If you manage WordPress sites and want fast, practical protection while you investigate or wait for an official plugin fix, our WP‑Firewall Basic free plan offers immediate, managed defenses. The free plan includes essential protection: a managed firewall, unlimited bandwidth, a WAF, malware scanning and mitigation for core OWASP Top 10 risks — powerful controls you can enable in minutes. These protections can stop unauthenticated reconnaissance attempts against plugins like WebP Express, reduce noise from automated scanners, and give you time to implement permanent fixes. Learn more or activate the free plan here: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

(If you need additional mitigation such as automatic malware removal, granular IP allow/deny lists, monthly reports or auto virtual patching, our Standard and Pro plans offer expanded controls to streamline management and incident response.)

---

Final recommendations and next steps

1. Check immediately if any of your sites run WebP Express (versions <= 0.25.9).
2. If you run the plugin, decide between temporary deactivation or applying webserver/WAF-based blocking for plugin endpoints.
3. Use a WAF with virtual patching capabilities (or enable the managed protections available through WP‑Firewall) to eliminate the attack surface while you patch.
4. Rotate any credentials that might have been exposed and audit logs for suspicious activity.
5. Implement longer-term controls: regular plugin updates, least privilege, and staging testing of updates.

We realize security advisories like this cause stress for site owners and administrators. Our goal at WP‑Firewall is to make that stress manageable — by providing practical, hands‑on mitigations and managed protections that give you time to implement permanent fixes without risking downtime or compromise.

If you have questions about how to apply the mitigations above to your specific hosting environment, or want help deploying virtual patches and tailored WAF rules, reach out to our support team through your WP‑Firewall dashboard.

— WP‑Firewall Security Team