Forms for Mailchimp by Optin Cat < 2.5.5 - Authenticated (Editor+) Stored Cross-Site Scripting

Description

The Forms for Mailchimp by Optin Cat plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the params_str function in versions up to, and including, 2.5.4 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with editor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.