Numerous Plugins and Themes from the AccessPress Themes (aka Access Keys) vendor are backdoored due to their website being compromised. Only plugins and themes downloaded via the vendor website are affected, and those hosted on wordpress.org are not. However, all of them were updated or removed to avoid any confusion
CWE-912 - Hidden Functionality
The software contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the software's users or administrators.