The W3 Total Cache plugin for WordPress is vulnerable to information exposure in all versions up to, and including, 2.9.3. This is due to the plugin bypassing its entire output buffering and processing pipeline when the request's User-Agent header contains "W3 Total Cache", which causes raw mfunc/mclude dynamic fragment HTML comments — including the W3TC_DYNAMIC_SECURITY security token — to be rendered in the page source. This makes it possible for unauthenticated attackers to discover the value of the W3TC_DYNAMIC_SECURITY constant by sending a crafted User-Agent header to any page that contains developer-placed dynamic fragment tags, granted the site has the fragment caching feature enabled.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v3.1