The PPWP – Password Protect WordPress | #1 Most-Reviewed Password Plugin plugin for WordPress is vulnerable to Insecure Direct Object Reference in all versions up to, and including, 1.9.20 via the ppw_free_set_password AJAX action due to missing validation on a user controlled key. This makes it possible for authenticated attackers, with Contributor-level access and above, to update the password on any password protected post and subsequently access the content.
Analyzing vulnerability vectors…