Categories: Hacking

Critical flaw in Yahoo allows Hacker to delete 1.5M records

Vulnerability in Yahoo allowed Egyptian hacker to delete more than 1 million and half records from Yahoo database. Yahoo immediately fixed it.

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

There are 5 parameters in the above URL

prop= category
fid= topic id
crumb = something like session
cid = Comment id
cmd= the method

He has found that changing the FID and CID parameter values he was able to delete other comments from the forum, even if posted by other users.

Deleting Posts

Ibrahim also discovered a similar problem testing the deletion mechanism, the HTTP Header POST request for deleting action appears as:

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.

Pierluigi Paganini

(Security Affairs – Yahoo, hacking)

Pierluigi Paganini

Pierluigi Paganini is member of the ENISA (European Union Agency for Network and Information Security) Threat Landscape Stakeholder Group and Cyber G7 Group, he is also a Security Evangelist, Security Analyst and Freelance Writer. Editor-in-Chief at "Cyber Defense Magazine", Pierluigi is a cyber security expert with over 20 years experience in the field, he is Certified Ethical Hacker at EC Council in London. The passion for writing and a strong belief that security is founded on sharing and awareness led Pierluigi to find the security blog "Security Affairs" recently named a Top National Security Resource for US. Pierluigi is a member of the "The Hacker News" team and he is a writer for some major publications in the field such as Cyber War Zone, ICTTF, Infosec Island, Infosec Institute, The Hacker News Magazine and for many other Security magazines. Author of the Books "The Deep Dark Web" and “Digital Virtual Currency and Bitcoin”.