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Vigil@nce - Microsoft Anti-Cross Site Scripting: information disclosure
January 2012 by Vigil@nce
This bulletin was written by Vigil@nce : http://vigilance.fr/offer
SYNTHESIS OF THE VULNERABILITY
When an ASP.NET web site uses the Microsoft AntiXSS library, an attacker can use an HTML document containing script code which is not filtered, and which can read information.
Severity: 2/4
Creation date: 11/01/2012
Revision date: 20/01/2012
IMPACTED PRODUCTS
Microsoft IIS
DESCRIPTION OF THE VULNERABILITY
The Microsoft Anti-Cross Site Scripting library is used by ASP.NET web sites to filter HTML documents, in order to remove forbidden scripts they contain.
The GetSafeHtml() and GetSafeHtmlFragment() function filter data. However, an attacker can use an escape character (\), in order to bypass this filtering. Malicious script code can then run in the context of the visitor’s browser.
When an ASP.NET web site uses the Microsoft AntiXSS library, an attacker can therefore use an HTML document containing script code which is not filtered, and which can read information.
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