One of the most famous vulnerabilities affecting this era of ASP.NET allowed attackers to decrypt and modify encrypted data, such as ViewState or authentication cookies. By observing the error messages returned by the server when malformed ciphertext was submitted, an attacker could eventually gain full administrative access.
"Internal apps don't need this fix." Truth: Insider threats and lateral movement (e.g., via phishing) mean internal apps are often the most vulnerable. x-aspnet-version 4.0.3 vulnerabilities
While this header was originally intended for debugging and compatibility purposes, in the hands of a malicious actor, it serves as a reconnaissance tool. It tells the attacker exactly which weapon to select from their arsenal. One of the most famous vulnerabilities affecting this
This vulnerability allowed attackers to bypass security features like <httpRuntime requestValidationMode="2.0"> by sending specially crafted requests, leading to information disclosure. While this header was originally intended for debugging
Successful exploitation leads to remote code execution (RCE) via deserialization of ObjectStateFormatter .