The Passster WordPress plugin before 3.5.5.8 does not escape the area parameter of its shortcode, which could allow users with a role as low as Contributor to perform Cross-Site Scripting attacks.

The Passster WordPress plugin before 3.5.5.9 does not properly check for password, as well as that the post to be viewed is public, allowing unauthenticated users to bypass the protection offered by the plugin, and access arbitrary posts (such as private) content, by sending a specifically crafted request.

The Passster WordPress plugin before 3.5.5.5.2 stores the password inside a cookie named "passster" using base64 encoding method which is easy to decode. This puts the password at risk in case the cookies get leaked.