CVE-2021-24537 – This vulnerability allows high-privilege WordPr... (How to Fix)

Q: What is the severity of CVE-2021-24537?

CVE-2021-24537 has a CVSS score of 7.2 (HIGH). This vulnerability allows high-privilege WordPress users (administrators/editors) to execute arbitrary PHP code via the Similar Posts plugin widget settings. It bypasses WordPress hardening measures like DISALLOW_FILE_EDIT and DISALLOW_FILE_MODS. Only WordPress sites using the vulnerable plugin are affected.

📋 TL;DR

This vulnerability allows high-privilege WordPress users (administrators/editors) to execute arbitrary PHP code via the Similar Posts plugin widget settings. It bypasses WordPress hardening measures like DISALLOW_FILE_EDIT and DISALLOW_FILE_MODS. Only WordPress sites using the vulnerable plugin are affected.

💻 Affected Systems

Products:

WordPress Similar Posts plugin

Versions: through 3.1.5

Operating Systems: All

Default Config Vulnerable: ⚠️ Yes

Notes: Requires high-privilege WordPress user account (administrator/editor)

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete site compromise leading to data theft, malware installation, defacement, or use as attack platform

🟠

Likely Case

Privileged user executes malicious code to modify content, steal data, or create backdoors

🟢

If Mitigated

Limited impact if proper user access controls restrict high-privilege accounts

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: LOW

Exploitation requires authenticated high-privilege user access

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 3.1.6 or later

Vendor Advisory: https://wpscan.com/vulnerability/0d6b46cb-5244-486f-ad70-4023907ac9eb

Restart Required: No

Instructions:

1. Update Similar Posts plugin to version 3.1.6 or later via WordPress admin panel. 2. Verify update completed successfully. 3. Test widget functionality.

🔧 Temporary Workarounds

Disable plugin

all

Temporarily disable Similar Posts plugin until patched

wp plugin deactivate similar-posts

Restrict user privileges

all

Limit number of users with administrator/editor roles

🧯 If You Can't Patch

Remove Similar Posts plugin completely
Implement strict user access controls and monitor administrator activities

🔍 How to Verify

Check if Vulnerable:

Check WordPress admin panel > Plugins > Similar Posts version. If version is 3.1.5 or earlier, system is vulnerable.

Check Version:

wp plugin get similar-posts --field=version

Verify Fix Applied:

Confirm Similar Posts plugin version is 3.1.6 or later in WordPress admin panel.

📡 Detection & Monitoring

Log Indicators:

Unusual PHP execution in widget settings
Administrator modifying similar-posts widget configurations
POST requests to /wp-admin/widgets.php with PHP code

Network Indicators:

HTTP POST requests containing PHP code to widget endpoints

SIEM Query:

source="wordpress.log" AND "widget_rrm_similar_posts_condition" AND ("eval" OR "base64_decode" OR "system")

📊 Metadata

CVE ID: CVE-2021-24537

CVSS v3 Score: 7.2 (HIGH)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-94

Published: November 8, 2021

Last Updated: November 21, 2024

🔗 References

https://wpscan.com/vulnerability/0d6b46cb-5244-486f-ad70-4023907ac9eb Exploit,Third Party Advisory
https://wpscan.com/vulnerability/0d6b46cb-5244-486f-ad70-4023907ac9eb Exploit,Third Party Advisory

📤 Share & Export

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🔗 Related Vulnerabilities

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