Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Request Validation (aka the ValidateRequest filters) in ASP.NET in Microsoft .NET Framework with the MS07-040 update does not properly detect dangerous client input, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated by a query string containing a "<~/" (less-than tilde slash) sequence followed by a crafted STYLE element.
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.