Pierluigi Paganini
March 01, 2014
The Egyptian cyber security expert Ibrahim Raafat has discovered a serious flaw in the Yahoo! website.
The hacker demonstrated on his blog how to exploit the “Insecure Direct Object Reference Vulnerability” vulnerability in the Yahoo! sub-domain (suggestions.yahoo.com) to delete all the posted thread and comments on Yahoo’s Suggestion Board website.
As demonstrated by Raafat it is possible to escalate user privileges that allow a hacker to delete more than 365,000 posts and 1,155,000 comments from Yahoo! Database. Following the video Proof-of-Concept for the Yahoo! vulnerability.
It is not first time that hackers discover a serious flaw in the websites managed by the company, last year for example another Egyptian experts, Ebrahim Hegazy @Zigoo0), has found Blind SQL Injection could lead to data leakage.
Technical details on how to exploit the flaw to delete comments and posts are available in the post published by the expert.
Deleting Comments
Ibrahim, while deleting his comment, has noticed the HTTP Header of POST request, i.e.
prop=addressbook&fid=367443&crumb=Q4.PSLBfBe.&cid=1236547890&cmd=delete_comment
prop= category
fid= topic id
crumb = something like session
cid = Comment id
cmd= the method
POST cmd=delete_item&crumb=SbWqLz.LDP0
but just appending the fid (topic id) parameter to the URL is possible to delete the respective post, anyone who has posted
POST cmd=delete_item&crumb=SbWqLz.LDP0&fid=xxxxxxxx
Ibrahim has reported the flaw to Yahoo Security team
Starting from the knowledge of the vulnerabilities also a novice hacker could write a script that interactively erases posts and comments from the Yahoo! sub-domain.
The vulnerability was reported to Yahoo! company that has fixed it and rewarded the expert with Bug Bounty.
(Security Affairs – Yahoo, hacking)
