Plugin-navn	Site Checkup AI Troubleshooting with Wizard and Tips for Each Issue
Type of Vulnerability	Log file poisoning
CVE Number	CVE-2025-11627
Hastighed	Medium
CVE Publish Date	2025-10-30
Source URL	CVE-2025-11627

Urgent: CVE-2025-11627 — Unauthenticated Log File Poisoning in Site Checkup Plugin (≤ 1.47) — What WordPress Site Owners and Developers Must Do Now

Forfatter: WP‑Firewall Security Team

Dato: 2025-10-30

Tags: wordpress, vulnerability, waf, incident-response, plugin-security

Oversigt: A Broken Access Control vulnerability (CVE-2025-11627) affecting the “Site Checkup — AI Troubleshooting with Wizard and Tips for Each Issue” plugin up to and including version 1.47 allows unauthenticated attackers to poison server-side log files. The vendor released a fixed version 1.48. This post explains the technical risk, how attackers abuse the flaw, practical detection and mitigation steps you can apply immediately (including virtual patching/WAF rules), developer fixes, and an incident response checklist. Written from the perspective of an experienced WordPress security team.

Table of contents

• Executive summary
• What “log file poisoning” means and why it matters
• What we know about CVE-2025-11627 (impact and exploitability)
• Indicators of compromise (IoCs) and how to detect exploitation
• Immediate site-owner actions (step-by-step)
• Virtual patch (WAF) rules you can deploy now — examples and explanations
• Sample ModSecurity rules and signature patterns
• Developer guidance — secure coding fixes for plugin authors
• Post-incident hardening and long-term mitigation
• Recovering from a compromise — incident response checklist
• How WP‑Firewall can help you right now (Free plan details & signup)
• Closing notes and resources

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Executive summary

A widely-used WordPress plugin (Site Checkup — AI Troubleshooting…) shipped an unauthenticated function that allows remote users to write arbitrary content into log files on disk. Attackers can abuse this to inject PHP code or other malicious payloads into logs, which in many hosting environments can later be executed through file inclusion or other misconfigurations. The issue is classified as Broken Access Control (OWASP A5) and has CVE-2025-11627.

Risk to site owners:

• Unauthenticated remote actors can place attacker-controlled data into files the web server can read.
• Depending on hosting and other plugin behavior, this can lead to remote code execution (RCE), full site compromise, data theft, SEO spam, or persistent backdoors.
• The plugin author fixed the issue in version 1.48. If you run 1.47 or earlier, update immediately. If you cannot update right now, apply the mitigations below.

This guide provides actionable, practical steps you can implement in minutes and longer-term developer fixes that should be applied upstream.

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What “log file poisoning” means and why it matters

“Log file poisoning” is when an attacker submits specially crafted data that ends up being written to server-side log files (application logs, debug logs, access logs, or plugin-specific logs). If an attacker can insert PHP (for example <?php ... ?>) or other executable content into a file that is later interpreted by PHP via an inclusion path or reachable through the webserver, this can become RCE.

Common exploitation chains:

1. Write PHP into a log file that is stored inside a web‑accessible directory.
2. Trigger a local file inclusion (LFI) or accidentally included log file via another plugin, theme, or misconfiguration.
3. Execute the PHP payload to get a shell, create backdoors, or escalate privileges.

Even when direct RCE is not possible, poisoned logs can be used to:

• Hide or persist backdoors,
• Inject SEO spam,
• Exfiltrate data,
• Confuse forensic efforts.

Because the vulnerability is unauthenticated in this case, the attack surface includes anyone on the internet.

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What we know about CVE-2025-11627 — impact and exploitability

• Type: Broken Access Control — unauthenticated log file poisoning
• Berørte versioner: <= 1.47
• Rettet i: 1.48
• CVE: CVE-2025-11627
• Reported: 30 Oct 2025
• Reported privileges: Ugodkendt
• CVSS (reported): 6,5 (Mellem)

Technical summary (high level, safe for public guidance):

• The plugin exposes an endpoint that accepts input from unauthenticated users.
• Input is appended/written to a log file without proper validation or authorization.
• The plugin does not properly validate the target file path, sanitize content, or restrict write permissions.
• Because the endpoint is unauthenticated, attackers can repeatedly append arbitrary strings to the log file.

Exploitability considerations:

• Writing arbitrary content into a file is straightforward for an attacker with direct access to the endpoint.
• Turning a poisoned log into RCE often requires a second vulnerability or misconfiguration (LFI, webserver misconfiguration, or another plugin including the log contents).
• However, in many shared or misconfigured environments, a poisoned log saved in a web-accessible or interpretable path can be executed directly.

Bottom line: treat this as a high-priority patch. Even though the CVSS is medium, the unauthenticated nature and potential to chain into RCE make it dangerous in practice.

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Indicators of compromise (IoCs) — what to look for now

Look for suspicious requests and suspicious lines in logs. Examples:

1. Unusual requests to plugin endpoints:
   • Any GET/POST calls to plugin paths or REST routes belonging to the Site Checkup plugin from unknown IPs outside normal traffic.
   • Examples (non-exhaustive):
     • /wp-admin/admin-ajax.php?action=site_checkup_*
     • /wp-json/site_checkup/v1/*
     • plugin-specific query parameters like log, file, content, path, message
2. Log file entries that contain:
   • PHP open tags: <?php
   • eval(, assert(, system(, passthru(, shell_exec(, base64_decode(
   • Long base64 blobs that look like payloads
   • Arbitrary HTML or JavaScript in places where logs normally contain clear-text messages
   • Repeated suspicious messages from the same IPs with payload-like content
3. New or modified files with weird timestamps:
   • Files created in wp-content/uploads/ eller wp-content/plugins/<plugin>/logs with modification times matching suspicious requests.
4. Webshell indicators:
   • Files or logs containing typical webshell patterns like $_REQUEST, preg_replace('/.*/e', eval(base64_decode(...)), or simple backdoor function calls.

Where to check:

• The plugin’s log files (if accessible via filesystem)
• Web server access logs and error logs (look for suspicious POSTs or encoded payloads)
• wp-indhold/uploads and other writable directories
• Database entries if the plugin stores logs or data in database tables

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Immediate site-owner actions — step-by-step

If you run the Site Checkup plugin version 1.47 or older, follow these steps immediately.

1. Update (preferred)
   Update the plugin to version 1.48 or later. This is the vendor-provided fix. Test on staging if possible, then update production as soon as possible.
2. If you cannot update immediately, temporarily disable the plugin
   Deactivate the plugin from Dashboard → Plugins.
   If you cannot access the Dashboard, rename the plugin folder via SFTP/SSH (wp-content/plugins/site-checkup → site-checkup.disabled).
3. Apply short-term WAF rules (see next section)
   Block requests to plugin endpoints that accept content for logs, and block patterns that include PHP tags or suspicious payloads.
4. Restrict file permissions for the plugin log directory
   Ensure logs are not web‑accessible. Move log files outside the web root or enforce strict ACLs.
   Recommended: files 640, directories 750, owner = web server user. Do not give world write/read.
5. Scan for IOCs and backdoors
   Search for files with <?php in upload directories, plugin directories, and log files. Look for recently modified files.
   Use your malware scanner and manual searches for common webshell signatures.
6. Rotate credentials and sessions
   Immediately reset admin passwords, database credentials if you suspect compromise, and rotate API keys/Tokens.
   Force logout all users (WordPress: change salts in wp-config.php or use a plugin to force session invalidation).
7. Backup
   Take a full backup before making major changes. Then take a clean backup after you remediate.
8. Notify stakeholders and, if necessary, your host
   If you suspect compromise, inform your hosting provider — they may help detect wider infra-level issues.

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Virtual patch (WAF) rules you can deploy now — strategy

If you cannot update immediately, virtual patching with a WAF is an effective stop-gap. A good rule set will:

• Block unauthenticated requests to plugin endpoints that write logs.
• Block payloads that include PHP tags, suspicious function names, or base64 blobs.
• Block attempts that include path traversal sequences (../).
• Enforce content-type validation (e.g., require JSON or application/x-www-form-urlencoded as expected).
• Rate-limit suspicious endpoints to slow automated attack attempts.

Below are example rule concepts and sample ModSecurity rules you can adapt.

High-level rule recommendations:

• Block any POST or GET with <?php eller <= in request body or parameters.
• Block requests with base64_decode( eller eval( in any parameter.
• Block path traversal sequences for parameters that seem to be file paths.
• Block or challenge requests to REST or AJAX endpoints used by the plugin if the request is unauthenticated.

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Sample ModSecurity rules and signature patterns

Note: adapt these to your environment and test on staging. These examples are patterns meant for immediate, conservative use.

1) Block PHP tags in request bodies or parameters
SecRule REQUEST_BODY|ARGS "@rx <\?(php|=)" \
  "id:1001001,phase:2,deny,log,status:403,msg:'Blocked request containing PHP tags (possible log poisoning attempt)'"

2) Block dangerous function names in parameters or body
SecRule ARGS|REQUEST_BODY "@rx (eval\(|base64_decode\(|system\(|shell_exec\(|passthru\()" \
  "id:1001002,phase:2,deny,log,status:403,msg:'Blocked suspicious PHP function in request (possible code injection)'"

3) Block path traversal attempts in file path parameters
SecRule ARGS_NAMES|ARGS "@rx (file|path|log|filename|target)" \
  "chain,id:1001003,phase:2,deny,log,status:403,msg:'Blocked path traversal parameter in plugin endpoint'"
SecRule ARGS "@rx \.\./" \
  "t:none"

4) Block likely webshell payloads encoded in Base64
SecRule ARGS|REQUEST_BODY "@rx (?:[A-Za-z0-9+/]{100,}={0,2})" \
  "id:1001004,phase:2,deny,log,status:403,msg:'Blocked long base64 blob in request (possible payload)'"

5) Block requests specifically targeting plugin endpoints (tune to actual endpoint)
SecRule REQUEST_URI "@beginsWith /wp-json/site_checkup" \
  "id:1001005,phase:1,deny,log,status:403,msg:'Blocked unauthenticated access to Site Checkup REST route'"

6) Rate limit suspicious endpoints (example using simple IP counting)
SecAction "id:1001006,phase:1,pass,nolog,initcol:ip=%{REMOTE_ADDR},setvar:ip.req_counter=+1"
SecRule IP:REQ_COUNTER "@gt 20" "id:1001007,phase:1,deny,status:429,log,msg:'Rate limit exceeded for endpoint'"

Important notes:

• Always test rules in detection-only (audit) mode first to avoid false positives.
• Use incremental deployment: start by logging and monitoring, then move to deny.
• Customize REQUEST_URI rules to match the plugin’s actual endpoints used by the vulnerable versions.

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WAF logic to prioritize (practical checklist)

• Block unauthenticated access to any endpoint that writes to disk.
• Block payloads that contain <?php or other server-side code markers.
• Block parameters containing ../ (path traversal).
• Block patterns with function names used for code execution (eval, system, etc.).
• Deploy rate limiting for endpoints that saw repeated attempts.
• Add an allowlist for your own admin IPs if feasible to reduce disruption.

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Developer guidance — how the plugin should be fixed (secure coding)

If you are a plugin developer or responsible for a theme/plugin that interacts with files, apply the following:

1. Add authorization checks

   if ( ! current_user_can( 'manage_options' ) ) {
       wp_send_json_error( 'Forbidden', 403 );
   }
   

   register_rest_route( 'site-checkup/v1', '/write-log', array(
     'methods'  => 'POST',
     'callback' => 'sc_write_log',
     'permission_callback' => function () {
         return current_user_can( 'manage_options' );
     },
   ) );
   

2. Validate and sanitize inputs

   $filename = sanitize_file_name( wp_unslash( $_POST['filename'] ?? '' ) );
   $content  = wp_kses_post( wp_unslash( $_POST['content'] ?? '' ) ); // or a stricter sanitizer
   

   Reject filenames with .., leading slashes, or absolute paths. Use realpath checks.

3. Restrict write location and avoid web‑accessible directories

   $log_dir = WP_CONTENT_DIR . '/site-checkup-logs';
   if ( ! file_exists( $log_dir ) ) {
       wp_mkdir_p( $log_dir );
   }
   $target = $log_dir . '/' . $filename;
   

   $real_base = realpath( $log_dir );
   $real_target = realpath( dirname( $target ) ) . '/' . basename( $target );
   if ( strpos( $real_target, $real_base ) !== 0 ) {
       wp_die( 'Invalid target path' );
   }
   

4. Avoid writing executable PHP content

   $content = str_replace( array(''), '', $content );
   

5. Use the WordPress Filesystem API where appropriate

   WP_Filesystem provides abstraction and aligns with different hosting setups.

6. Logging best practices
   • Use structured logs: timestamps, sanitized fields.
   • Rotate logs and limit size.
   • Ensure logs are owned by appropriate user and have strict permissions.
7. Nonce and CSRF protection (for AJAX/admin forms)

   if ( ! wp_verify_nonce( $_REQUEST['_wpnonce'] ?? '', 'site_checkup_action' ) ) {
       wp_send_json_error( 'Invalid nonce', 403 );
   }
   

8. Limit user-supplied content length

   Cap content length to reasonable values and reject extremely long payloads.

By combining authorization checks, input sanitation, path validation, and careful write location decisions, you eliminate the log poisoning vector.

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Post-incident hardening — actions after remediation

• Re-scan your site with a reliable malware scanner.
• Perform file integrity checks against a known-good backup.
• Review server and access logs for evidence of exploitation.
• Remove or sanitize any poisoned logs found. If you suspect logs contained PHP and were accessible, treat the site as potentially compromised and investigate thoroughly.
• Reset all administrative passwords and secrets.
• Rotate API keys, tokens, and database credentials as necessary.
• Harden PHP and webserver configuration (disable execution in upload directories, restrict open_basedir, disable risky PHP functions).
• Set up a monitoring and alerting program for new vulnerabilities affecting installed plugins.

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Recovering from a compromise — incident response checklist

If you find evidence a site was exploited, follow a controlled process:

1. Contain
   • Take the site offline or put it in maintenance mode.
   • Isolate the affected host if possible.
2. Preserve evidence
   • Take files and database snapshots for forensic work before overwriting anything.
3. Eradicate
   • Replace infected files with clean copies from backups or latest plugin/theme versions.
   • Remove unauthorized users and scheduled tasks (crons).
   • Remove any suspicious PHP code in logs or uploads.
4. Recover
   • Restore from a clean backup if you have one and are confident it predates the compromise.
   • Re-apply updates (WordPress core, plugins, themes).
   • Re-enable services and monitor carefully.
5. Learn
   • Conduct a root-cause analysis: how did the attacker get in? Were there other vulnerabilities?
   • Implement lessons learned (hardening, monitoring, processes).

If you’re not comfortable completing these steps yourself, contact a professional incident response service.

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How WP‑Firewall helps you protect immediately

Start protecting your site the fast way — WP‑Firewall Free Plan

If you need immediate protection while you verify and remediate, WP‑Firewall’s Free plan provides essential automated defenses you can enable in minutes. The Free plan includes:

• Managed firewall and WAF rules (virtual patching for known vulnerabilities)
• Unlimited bandwidth for protection
• Malware scanner to detect poisoned logs and webshells
• Mitigations for the OWASP Top 10 (including broken access control vectors)

Sign up for the Free plan and get protection configured quickly: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

(If you need more advanced automated remediation — automatic malware removal, blacklisting/whitelisting IPs, monthly security reports, and auto virtual-patching — our Standard and Pro plans are available. But the Free plan gives you immediate basic protection and detection while you update plugins and perform checks.)

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Final notes and practical reminders

• Update plugin to version 1.48 or later NOW. This is the single most effective step.
• If you cannot apply the vendor fix immediately, apply WAF rules and/or deactivate the plugin.
• Treat any signs of log poisoning seriously — it often precedes or accompanies more severe compromise activity.
• For developers: enforce permissions, sanitize everything, avoid writing untrusted input to disk within web-accessible paths, and follow the WordPress Security Coding standards.
• Enable logging and keep backups — they are your lifeline if something goes wrong.

If you’d like help writing and deploying the precise WAF rules above, verifying your environment for indicators of compromise, or virtual patching until you can update, our team at WP‑Firewall can assist. Sign up for a Free plan to get initial protection and scanning right away: https://my.wp-firewall.com/buy/wp-firewall-free-plan/

Stay safe — treat unauthenticated file write vulnerabilities with high priority. Unchecked, they are one of the fastest paths to site compromise.

— WP‑Firewall Security Team

References and further reading

• CVE-2025-11627 (public record)
• WordPress Security Best Practices: nonces, capability checks, Filesystem API
• OWASP Top Ten — Broken Access Control

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If you want, I can:

• Provide a deployable set of ModSecurity rules tuned to your site,
• Generate a quick checklist you can paste into your helpdesk,
• Walk through a command-line scan for IoCs specific to your hosting environment.