Pierluigi Paganini March 29, 2023

OpenAI addressed multiple severe vulnerabilities in the popular chatbot ChatGPT that could have been exploited to take over accounts.

OpenAI addressed multiple severe vulnerabilities in ChatGPT that could have allowed attackers to take over user accounts and view chat histories.

One of the issues was a “Web Cache Deception” vulnerability reported by the bug bounty hunter and Shockwave founder Gal Nagli, it could lead to an account takeover.

The expert discovered the vulnerability while analyzing the requests that handle ChatGPT’s authentication flow. The following GET request caught the attention of the expert:

https://chat.openai[.]com/api/auth/session

“Basically, whenever we login to our ChatGPT instance, the application will fetch our account context, as in our Email, Name, Image and accessToken from the server, it looks like the attached image below” Nagli wrote on Twitter detailing the bug.

The expert explained that to exploit the flaw, a threat actor can craft a dedicated .css path to the session endpoint (/api/auth/session) and send the link to the victim. Upon visiting the link, the response is cached and the attacker can harvest the victim’s JWT credentials and take full control over his account.

Nagli praised the OpenAI security team that quickly addressed the issue by instructing the caching server to not catch the endpoint through a regex.

The bad news is that the mitigation implemented by the company only partially addressed the issue. The researcher Ayoub Fathi discovered that it is possible to bypass authentication targeting another ChatGPT API. An attacker can exploit this bypass technique to access to a user’s conversation titles.

“GET /backend-api/conversations%0A%0D-testtest.css?offset=0&limit=20 Send it to a victim, and upon accessing it – his own “API” response will be cached, and if you recheck the same URL (i.e. fetching the cached response of the victim), you will be able to see the victim’s HTTP response, which contains the conversations’ titles.” explained the expert Ayoub Fathi on Twitter.

The expert pointed out that all ChatGPT APIs were vulnerable to the bypass, which means that an attacker could exploit the issue to read conversation titles, full chats, and account status.

Fathi reported the issue to OpenAI which quickly addressed it.

Unfortunately for the researchers, OpenAI has yet to run a bug bounty program to reward researchers that report vulnerabilities in its chatbot.

On Friday, OpenAI revealed that the recent exposure of users’ personal information and chat titles in its chatbot service was caused by a bug in the Redis open-source library.

The company identified the bug and quickly addressed it.

“We took ChatGPT offline earlier this week due to a bug in an open-source library which allowed some users to see titles from another active user’s chat history. It’s also possible that the first message of a newly-created conversation was visible in someone else’s chat history if both users were active around the same time.” reads an update published by the company.

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Pierluigi Paganini

(SecurityAffairs – hacking, ChatGPT)