Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Text_Filter/lib/Horde/Text/Filter/Xss.php in Horde Application Framework before 3.3.6, Horde Groupware before 1.2.5, and Horde Groupware Webmail Edition before 1.2.5 does not properly handle data: URIs, which allows remote attackers to conduct cross-site scripting (XSS) attacks via data:text/html values for the HREF attribute of an A element in an HTML e-mail message. NOTE: the vendor states that the issue is caused by "an XSS vulnerability in Firefox browsers."
CWE-79 - Cross Site Scripting
Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.