We are seeing reports that a vulnerability in the Absolute Privacy WordPress plugin (link) is being used to hack and compromise sites with it installed.
This plugin has a serious unpatched security vulnerability that allows anyone to login in the WordPress site without a password. From Secunia:
Schaffnern has discovered a vulnerability in the Absolute Privacy plugin for WordPress, which can be exploited by malicious people to bypass certain security restrictions.
The vulnerability is caused due to an error within the “abpr_authenticateUser()” function in wp-content/plugins/absolute-privacy/functions.php, which prevents the password from being verified. This can be exploited to bypass the authentication mechanism and gain administrative access to the application.
The vulnerability is confirmed in version 2.0.5. Other versions may also be affected.
Note that this plugin has had more than 35 thousand downloads and no patches for this bug. We recommend deleting this plugin asap until a fix is in place.
Our team is still analysing this vulnerability and we will post more details soon. Additional information and original report was found here.
If you think your site has been compromised, you can verify it in here: http://sitecheck.sucuri.net