W3 Total Cache <= 2.8.12 - Unauthenticated Command Injection

The W3 Total Cache plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 2.8.12 via _parse_dynamic_mfunc . This makes it possible for unauthenticated attackers to execute code on the server when comments are enabled and a post has been incorrectly injected with the mfunc tags. Please note we consider this to be a theoretical issue, and as such we rejected the original report from the researcher who then submitted this to WPScan. WPScan assigned a CVE ID, but we do not agree that this is a true security vulnerability. Exploitation of this issue is theoretical and requires gaining access to a secret value much like gaining access to a password.

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. None of that substitutes for the fix: W3 Total Cache 2.8.13 closes this, and updating the plugin is the step that ends it.

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