e107 CMS before 2.3.13 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to inject malicious HTML by manipulating the author GET parameter in search.php, which is parsed with parse_str() and concatenated unescaped into a rendered input tag via the form handler's 'other' option key. Attackers can craft a single GET request containing a crafted author parameter to break out of the HTML input tag and inject an img element with an onerror handler, executing arbitrary JavaScript in the victim's browser session.