W3 Total Cache < 2.1.4 - Reflected XSS in Extensions Page (Attribute Context)

The plugin was vulnerable to a reflected Cross-Site Scripting (XSS) security vulnerability within the "extension" parameter in the Extensions dashboard, which is output in an attribute without being escaped first. This could allow an attacker, who can convince an authenticated admin into clicking a link, to run malicious JavaScript within the user's web browser, which could lead to full site compromise.

https://example.com/wp-admin/admin.php?page=w3tc_extensions&extension=%22%3E%3Cscript%3Ealert%281%29%3C%2Fscript%3E