Google has updated its Blogger feature to fix a flaw in its system that could potentially allow any individual to post an article on any website hosted using Blogger’s architecture . The critical flaw was found out by an Egyptian security expert Mazen Gamal Mesbah (@MazenGamal). He discovered a critical CSRF (Cross-site request forgery) vulnerability in the default share buttons under a blogspot post which could be utilized to hijack the blogspot.
Below the steps followed by the Mesbah to discover the flaw:
- I found the vulnerability in Button of Share Articles in blog as shown in the following picture.
- When I noticed this button I decided to investigate the possible presence of a flaw affecting it.
- When I click on Blogger Share button I noticed the CSRF token the Request, then I tried to bypass the mechanism of authentication based on it.
- I succeeded in the trick.
- Once verified the presence of the flaw I wrote an exploit file that could be used against any blog just knowing the Blog ID.
- The Blog ID is easy to retrieve, I discovered an easy way to access it.
- Once completed the exploit I tested it against the Blogger platform and I verified that it was working.
The timeline for the above vulnerability is reported below:
2/9/2014 – The vulnerability was found and report by Mazen Gamal Mesbah to Google.
2/9/2014 – Response received from the Blogger team acknowledging the vulnerability
3/9/2014 – The vulnerability was patched
4/9/2014 – A reward aka bounty of $3133.7 was received by the researcher for pointing out the vulnerability
Mesbah has uploaded a video detailing how he found out the vulnerability, which is given below :
Resource : Security Affairs.