One of the most popular WordPress Plugin called "W3 Total Cache" which is used to Improve site performance and user experience via caching, having potential vulnerability. On Christmas day, someone disclose it on full-disclosure site that how a plugin misconfiguration leads to possible WordPress cms hack.
The loophole is actually activated on the fact that how W3TC stores the database cache. Jason disclosed that cache data is stored in public accessible directory, from where a malicious attack can can retrieve password hashes and other database information.
Default location where this plugin stores data is "/wp-content/w3tc/dbcache/" and if directory listing is enabled, attacker can browse and download it.
He said,"Even with directory listings off, cache files are by default publicly downloadable, and the key values / file names of the database cache items are easily predictable."
Because the plugin is very famous ,so this makes quite easy for hackers to play with WordPress blogs. Author also publish a simple shell script to identify and exploit this bug.
We would like to recommend webmasters to either upgrade the plugin to new version or deny access to plugin directory by making an extra .htccess in that folder.