Linksys WRT54G Cross Site Scripting

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Description of Vulnerability:  
- -----------------------------  
Linksys WRT54G is a consumer wireless G broadband router and four port  
switch (http://www.linksysbycisco.com/ANZ/en/support/WRT54G). The  
device provides an administration interface for configuration via a web  
browser. Unfortunately the interface does not sanitize keywords for  
safe browsing leading to a stored/persistent cross site scripting (XSS)  
vulnerability.  
  
Systems affected:  
- -----------------  
Cisco Linksys Wireless G Boradband Router WRT54G with firmware version  
4.21.1 was tested and found to be vulnerable.  
  
Proof of Concept:  
- -----------------  
1. Log into the WRT54G administration screen and navigate to /Filters.asp  
2. Enter "' onBlur='alert("xss")" for the "Website Blocking by Keyword"  
value.  
3. Click the 'Save Settings' button at the bottom of the form, ignore  
the error and click 'Continue'  
4. After the page refreshes click on the "Website Blocking by Keyword"  
textfield then click outside to view the JavaScript alert  
  
- --   
Justin Klein Keane  
http://www.MadIrish.net  
  
The digital signature on this e-mail may be confirmed using the  
PGP key located at: http://www.madirish.net/gpgkey  
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