Microsoft ASP.NET is prone to a cross-site scripting vulnerability because the software fails to properly sanitize user-supplied input before it is rendered in the browser of an unsuspecting user in the context of the affected site. An attacker may leverage this issue to have arbitrary script code execute in the browser of an unsuspecting user, with the privileges of the victim user's account. This may help the attacker steal cookie-based authentication credentials, retrieve sensitive information, and launch other attacks.
Block external access at the network boundary, unless external parties require service.
Filter access to the affected computer at the network boundary if global access isn't required. Restricting access to only trusted computers and networks might greatly reduce the likelihood of a successful exploit.
Run all software as a nonprivileged user with minimal access rights.
Attackers may successfully exploit client flaws in the browser through cross-site scripting vulnerabilities. When possible, run client software as regular user accounts with limited access to system resources. This may limit the immediate consequences of client-side vulnerabilities.
Do not follow links provided by unknown or untrusted sources.
Web users should be cautious about following links to sites that are provided by unfamiliar or suspicious sources. Filtering HTML from emails may help remove a possible vector for transmitting malicious links to users.
Set web browser security to disable the execution of script code or active content.
A successful exploit of cross-site scripting issues often requires executing malicious script code in web clients; consider disabling support for script code and active content within a client browser. Note that this mitigation tactic might adversely affect legitimate websites that rely on the execution of browser-based script code.
The vendor has released fixes to address this issue; please see the reference section for details.