Egyptian Cyber Security Analyst, 'Ibrahim Raafat', found and demonstrated 'Insecure Direct Object Reference Vulnerability' in Yahoo's website on his blog.
Exploiting the flaw escalates the user privileges that allow a hacker to delete more than 365,000 posts and 1,155,000 comments from Yahoo! Database. Technical details of the vulnerability are as explained below:
Deleting Comments: While deleting his own comment, Ibrahim noticed the HTTP Header of POST request, i.e.
prop=addressbook&fid=367443&crumb=Q4.PSLBfBe.&cid=1236547890&cmd=delete_comment
Where parameter 'fid' is the topic id and 'cid' is the respective comment ID. While testing, he found changing the fid and cid parameter values allow him to delete other comments from the forum, that are actually posted by another user.
Deleting Posts: Next, he also tested post deletion mechanism and found a similar loophole in that. A normal HTTP Header POST request of deleting a post is:
He found that, appending the fid (topic id) variable to the URL allows him to delete the respective post, that was not posted by himself i.e.Deleting Posts: Next, he also tested post deletion mechanism and found a similar loophole in that. A normal HTTP Header POST request of deleting a post is:
POST cmd=delete_item&crumb=SbWqLz.LDP0
POST cmd=delete_item&crumb=SbWqLz.LDP0&fid=xxxxxxxxIbrahim has reported the flaw to Yahoo Security team and also provided a Video Demonstration, as shown below:
A potential attacker with little knowledge of programming could write an automated script to delete all the comments and posts.
The vulnerability hunter claimed that he had received the Bug Bounty for reporting this security flaw to yahoo and which now has been fixed by the company.
