Missing Authorization vulnerability in Caseproof, LLC Memberpress allows Accessing Functionality Not Properly Constrained by ACLs.This issue affects Memberpress: from n/a through 1.11.34.

The Memberpress plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the 'mepr_screenname' and 'mepr_key' parameter in all versions up to, and including, 1.11.29 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.

The Memberpress plugin for WordPress is vulnerable to Blind Server-Side Request Forgery in all versions up to, and including, 1.11.29 via the 'mepr-user-file' shortcode. This makes it possible for authenticated attackers, with Contributor-level access and above, to make web requests to arbitrary locations originating from the web application and can be used to query and modify information from internal services.

The Memberpress plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘arglist’ parameter in all versions up to, and including, 1.11.29 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with Contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Memberpress plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the ‘message’ and 'error' parameters in all versions up to, and including, 1.11.26 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link. Note - the issue was partially patched in 1.11.25, but could still potentially be exploited under some circumstances.