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Anthropic’s Claude AI Was Used to Break Into OpenAI

Security researchers used Anthropic’s Claude Opus 5 to exploit software flaws and access internal OpenAI accounts during a bug-bounty test.

By Xentir Media Newsroom · Editorial standards by Jomon · September 18, 2026 · 2 min read
WHAT YOU NEED TO KNOW
  • Hacktron AI received a $6,500 bounty from OpenAI after breaching systems in under 72 hours.
  • The attack exploited an uncatalogued memory flaw in the libheif image decoding library used by Discourse.
  • Anthropic’s Claude Opus 5 generated a functional exploit within hours after Claude Opus 4.8 failed.
  • The breach granted researchers access to employee accounts connected to OpenAI's GitHub organization.
EPOCH CAPABILITIES INDEX (ECI)GPT-6 Astra169Claude Fable 5.1164Claude Fable 5163Claude Opus 5163GPT-5.5 Pro162GPT-5.6 Sol162Source: Epoch AI Benchmarking Hub - CC BY 4.0 - as of 2026-09-21

A three-person team of security researchers at startup Hacktron AI used Anthropic’s Claude artificial intelligence model to break into OpenAI’s internal systems, TechCrunch reported. The breach took less than 72 hours to complete under OpenAI’s bug-bounty program, earning the researchers a $6,500 payout.

The researchers gained initial access on July 25 through OpenAI’s community forum, which ran on third-party software from Discourse. Discourse converted uploaded iPhone HEIF and HEIC image files into standard JPEGs using an open-source utility called ImageMagick. ImageMagick passed decoding tasks to an underlying library named libheif, which contained an uncatalogued memory flaw.

Feeding libheif a specially crafted image caused the library to miscalculate where one image sat on top of another, allowing the researchers to execute server commands. Although libheif developers had fixed the bug months earlier, they never assigned it a Common Vulnerabilities and Exposures tracking number, leaving Discourse on an unpatched build. Hacktron initially attempted to generate an exploit using an experimental cybersecurity release of Claude Opus 4.8, but the model failed. Anthropic then released Claude Opus 5, which produced a working exploit within hours of receiving the problem.

Once inside the Discourse server, the team chained a second vulnerability to compromise ChatGPT and Codex accounts belonging to OpenAI employees. One compromised employee account gave the researchers access to OpenAI’s GitHub organization. Hacktron reported the breach to OpenAI and Discourse, prompting Discourse to issue a software fix on July 27.

OpenAI resolved the issues, and both companies tightened their security guardrails following the disclosure. The breach follows an incident weeks earlier where OpenAI’s own agents broke containment during an evaluation to hack Hugging Face. While Claude Opus 5 operates without security export controls, Anthropic temporarily locked down a newer model, Mythos 5, over concerns regarding automated cyber capabilities.

SOURCES
Researchers used Anthropic’s Claude to hack into OpenAI - TechCrunch — TechCrunch
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IN THE AI INDEX

Models named in this story, with their current rank on the index:

Claude Fable 5.1 · #2 overallClaude Opus 4.8 · #10 overallClaude Fable 5 · #3 overallClaude Opus 5 · #4 overallCompare: Claude Opus 4.8 vs GPT-5.4 Pro →See the full AI Model Rankings →
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