AppSec Blog

Bypassing ValidateRequest in ASP.NET

In this post, I am going to explain another technique that can be used to bypass the Validate Request filter in an html element context. This technique uses a different character encoding to bypass the blacklist checks that are done. To recap, ValidateRequest returns false when the following conditions are met:


Spot the Vuln - Grammys

The last thing I want is to walk into my house after a long day and see all the Grammys and awards. It would make me feel weird. Alicia Keys Spot the Vuln uses code snippets from open source applications to demonstrate vulnerabilities in real world web applications. Every Monday morning a vulnerable code snippet … Continue reading Spot the Vuln - Grammys


Spot the Vuln - Writing - Fake XSS and XSRF

Details Affected Software: EOF-0x01 Fixed in Version: ? Issue Type: XSS and XSRF Original Code: Found Here Details This week, we had a couple of bugs here affecting EOF-0x01 Command and Control. A red herring is the use of echo($_POST['pw']); to build HTML markup. Upon first glance, this seems like a straight forward XSS bug. … Continue reading Spot the Vuln - Writing - Fake XSS and XSRF


ASP.Net 4: Change the Default Encoder

In ASP.Net 4.0, Microsoft added the ability to override the default encoder. This is specifically focused on the HTMLEncode, HTMLAttributeEncode, and URLEncode functionality. These functions are used, in the eyes of security, to help mitigate cross-site scripting (XSS). The problem with the built in .Net routines is that they are built on a black-list methodology, … Continue reading ASP.Net 4: Change the Default Encoder


Spot the Vuln - Writing

Writing is a struggle against silence. Carlos Fuentes Spot the Vuln uses code snippets from open source applications to demonstrate vulnerabilities in real world web applications. Every Monday morning a vulnerable code snippet is posted. Take a look at the vulnerable code and try to identify where the security vulnerability is. Every Friday, a solution … Continue reading Spot the Vuln - Writing