# Mercor data breach: what happened and what to ask > The Mercor data breach of March 2026 came through a poisoned LiteLLM release. What was reported, what Mercor says, and what a company owner should ask. By Matt Burns, Vaultfish. Canonical: https://vaultfish.com/answers/mercor-data-breach Published: 2026-08-25 Updated: 2026-10-14 ## The short answer The Mercor data breach of March 2026 started with a bad update to LiteLLM, a free open-source tool. The bad code stole login keys. The Next Web reported about 4 TB taken and said thousands of companies were hit. Mercor says harm to customer information was very limited. [Mercor](/buyers/mercor) hires experts to train AI models. Its data arm buys workplace data. Its breach is the best-documented security incident at an AI data buyer so far, which is why owners keep asking about it. The reported data was about contractors and applicants. No company-archive data was reported exposed. > **Once you share records, they sit inside the buyer's systems.** It's like renting out a room. You keep the house, but you still ask who else has a key. ## What happened in the Mercor breach? Someone spread bad versions of LiteLLM, an open-source library. The code was built to pull credentials from any system that installed it, according to Mercor's own [incident update](https://www.mercor.com/blog/update-on-mercor-security-incident/). [The Next Web](https://thenextweb.com/news/meta-mercor-breach-ai-training-secrets-risk) reported that a group called TeamPCP made the first break-in. Lapsus$ claimed responsibility and tried to auction the data. [Hausfeld](https://www.hausfeld.com/what-we-do/current-claims/mercor-data-breach), a law firm, dates the incident to about 24 Mar 2026. The Next Web, citing court filings and the hackers' own claims, put the haul at about 4 TB. That included roughly 939 GB of source code, a 211 GB user database and about 3 TB of video and identity-verification data. TNW counted over 40,000 current and former contractors and customers. Names and Social Security numbers were among the data. Treat the sizes and counts as reports. Mercor confirms the poisoned release hit it. It says the impact was "very limited." ## What does Mercor say it did? Mercor says it audited third-party dependencies, rotated credentials and access keys, and applied stricter cloud security policies. It also added 24/7 managed detection and response. It hired Google Mandiant and Latacora for forensics. It offered affected people TransUnion identity protection. Mercor also says experts saw only a small subset of exposure, customer information impact was very limited and employees were unaffected (Mercor, incident update, self-reported). ## What came after? A putative class action, *Ananthula v. Mercor.io Corp.*, No. 3:26-cv-03362, was filed on 21 Apr 2026 in the Northern District of California. It alleges failure to implement reasonable security and violations of privacy law ([Hausfeld](https://www.hausfeld.com/what-we-do/current-claims/mercor-data-breach)). None of it is proven. The breach suits were consolidated before Judge William H. Orrick on 19 May 2026 and stayed pending mediation on 21 Jul 2026, per the [CourtListener docket](https://www.courtlistener.com/docket/73129103/deboni-v-mercorio-corporation/). Where it stands now is in [is Mercor legit](/answers/is-mercor-legit). TNW reported that Meta paused its work with Mercor indefinitely and that OpenAI was investigating. Figure: steps Poisoned LiteLLM release -> Credentials taken, about 4 TB reported -> Class action filed 21 Apr 2026. Mercor traces its March 2026 breach to a poisoned LiteLLM release, and a class action followed in April. ## What does it mean for a company licensing data? The case shows how much a buyer's pipeline can hold in one place. Put these questions in writing before you share a record: - Does the buyer connect to your accounts, or do you export the files? Mercor's [data page](https://www.mercor.com/data/) describes 100+ connectors. Troveo says it needs no OAuth into your systems (its own page). - What does the SOC 2 claim cover? Ask for the scope, the auditor, the test period and the date. Jackson Lewis, a law firm, advises reading those details instead of accepting the label. - Who sees raw data, and how long does the buyer keep it? - If a breach reaches your records, who notifies and who pays? See [who is liable if the data buyer is hacked](/answers/who-is-liable-if-the-data-buyer-is-hacked). _Security questions are free. Ask all of them. Buyers hear them every day._ More on the company is in [is Mercor legit](/answers/is-mercor-legit) and [Mercor data licensing](/answers/mercor-data-licensing). The [rights check](/rights-check) and the [risks page](/risks) cover the rest of the owner's side. Have a lawyer read any contract before you sign. They like that. _Vaultfish helps you run the process. We are not lawyers and this is not legal advice. If you need counsel who knows this area, we can point you to one._ ## Sources - [incident update](https://www.mercor.com/blog/update-on-mercor-security-incident/) - [The Next Web](https://thenextweb.com/news/meta-mercor-breach-ai-training-secrets-risk) - [Hausfeld](https://www.hausfeld.com/what-we-do/current-claims/mercor-data-breach) - [CourtListener docket](https://www.courtlistener.com/docket/73129103/deboni-v-mercorio-corporation/) - [data page](https://www.mercor.com/data/) - [Time](https://time.com/article/2026/08/25/google-spirit-airlines-ai-data-RL/) - [BigGo](https://finance.biggo.com/news/d34746c0-e437-4855-93c5-09c6e850550d) Our only referral relationship is with micro1, an AI data company. It may pay us a fee if a company we introduce goes ahead with it. You pay nothing extra. [How we are paid](https://vaultfish.com/disclosure)