Microsoft .NET Framework 1.1 SP1, 2.0 SP1 and SP2, 3.5, 3.5 SP1, 3.5.1, and 4.0, as used for ASP.NET in Microsoft Internet Information Services (IIS), provides detailed error codes during decryption attempts, which allows remote attackers to decrypt and modify encrypted View State (aka __VIEWSTATE) form data, and possibly forge cookies or read application files, via a padding oracle attack, aka "ASP.NET Padding Oracle Vulnerability."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A12365
https://exchange.xforce.ibmcloud.com/vulnerabilities/61898
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2010/ms10-070
http://www.vupen.com/english/advisories/2010/2751
http://www.vupen.com/english/advisories/2010/2429
http://www.securityfocus.com/bid/43316
http://weblogs.asp.net/scottgu/archive/2010/09/18/important-asp-net-security-vulnerability.aspx
http://threatpost.com/en_us/blogs/new-crypto-attack-affects-millions-aspnet-apps-091310
http://securitytracker.com/id?1024459
http://secunia.com/advisories/41409
http://pentonizer.com/general-programming/aspnet-poet-vulnerability-what-else-can-i-do/
http://isc.sans.edu/diary.html?storyid=9568
http://blogs.technet.com/b/srd/archive/2010/09/17/understanding-the-asp-net-vulnerability.aspx