Stored XSS in WP 404 Auto Redirect Plugin Allows Admin Script Injection

Compliance Impact

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Executive Summary

The WP 404 Auto Redirect to Similar Post plugin for WordPress has a Stored Cross-Site Scripting (XSS) vulnerability in all versions up to and including 1.0.5. This vulnerability arises because the plugin does not properly sanitize input or escape output in the admin settings. As a result, authenticated users with administrator-level permissions or higher can inject malicious web scripts into pages. These scripts will execute whenever any user accesses the affected page.

This vulnerability specifically affects multi-site WordPress installations and installations where the unfiltered_html capability has been disabled.

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Impact Analysis

This vulnerability can allow attackers with administrator privileges to inject malicious scripts that execute in the browsers of users visiting the affected pages. This can lead to unauthorized actions such as stealing user credentials, hijacking user sessions, defacing websites, or distributing malware.

Because the vulnerability is a Stored Cross-Site Scripting issue, the malicious code persists on the server and affects every user who accesses the injected page, increasing the potential impact.

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Detection Guidance

This vulnerability affects the WP 404 Auto Redirect to Similar Post plugin for WordPress in versions up to and including 1.0.5, specifically on multi-site installations or where unfiltered_html is disabled. Detection involves verifying the plugin version and configuration.

• Check the installed version of the WP 404 Auto Redirect to Similar Post plugin to see if it is version 1.0.5 or earlier.
• Confirm if the WordPress installation is multi-site or if unfiltered_html is disabled, as the vulnerability only affects these setups.
• Look for suspicious or unexpected scripts injected in admin settings pages or pages generated by the plugin.
• Use WordPress CLI commands to list plugin versions, for example: `wp plugin list --status=active` to identify the plugin version.
• Manually inspect the plugin's admin settings pages for injected scripts or unusual content.

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Mitigation Strategies

To mitigate this vulnerability, the primary step is to update the WP 404 Auto Redirect to Similar Post plugin to a version later than 1.0.5 where the issue is fixed.

• Upgrade the plugin to version 1.0.6 or later, as indicated by the plugin repository logs.
• Restrict administrator-level permissions to trusted users only, since exploitation requires authenticated admin access.
• If immediate update is not possible, consider disabling the plugin temporarily, especially on multi-site installations or where unfiltered_html is disabled.
• Review and sanitize any admin settings pages for injected scripts and remove any suspicious content.

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