The Custom Twitter Feeds plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to and including 2.5.4. This is due to insufficient output escaping in the CTF_Display_Elements::get_post_text() function when rendering cached tweet text. The plugin's ctf_get_more_posts AJAX action is available to unauthenticated users and directly outputs cached tweet data through nl2br() without HTML escaping. When an attacker can get malicious content into cached tweet data (either by tweeting content that gets cached by the site's feed configuration, or through other vulnerabilities), the malicious HTML/JavaScript is executed when the unauthenticated endpoint is accessed. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses the affected endpoint.