Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
An issue was discovered on Accellion FTA devices before FTA_9_12_180. There is XSS in courier/1000@/index.html with the auth_params parameter. The device tries to use internal WAF filters to stop specific XSS Vulnerabilities. However, these can be bypassed by using some modifications to the payloads, e.g., URL encoding.
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.