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Researchers Use Claude Opus 5 to Hack OpenAI Forum and Reach Internal Repositories

Researchers used Claude Opus 5 to build a libheif exploit that compromised OpenAI's forum, hijacked employee ChatGPT/Codex accounts, and reached the internal monorepo.

On July 25, 2026, Hacktron researchers used Anthropic's Claude Opus 5, released the day before, to produce a working exploit for a libheif 1.19.7 heap-buffer overflow (CVE-2026-32882, DSA-6417-1) reached through HEIC/HEIF uploads that bypassed FastImage checks in OpenAI's Discourse forum, achieving RCE in about three hours after Claude Opus 4.8 failed under ASLR. A separate OpenAI SSO misconfiguration converted the compromised forum session into a no-interaction takeover of employees' ChatGPT and Codex accounts, from which researchers opened harmless pull request 1186742 in the private openai/openai monorepo to prove access. OpenAI fixed the issue roughly 14 hours after disclosure and awarded $6,500; Discourse published GHSA-vhm9-85gw-x335 on July 28.

Cyber Security Newsupdated · 1h agofirst · 12h agoExploit / PoC in the wild 10 sourcesCVE-2026-32882

Related CVEs

  • CVE-2026-328827.1<1%
    libheif is a HEIF and AVIF file format decoder and encoder.
    libheif is a HEIF and AVIF file format decoder and encoder. Versions 1.21.2 and prior contain a heap buffer over-read in HeifPixelImage::overlay() in libheif/pixelimage.cc. When compositing an overlay image (iovl) whose child image has a different bit depth for the alpha channel than for the color channels, the function indexes into the alpha plane using the color channel stride (in_stride) instead of the previously retrieved alpha_stride, causing reads past the end of the alpha buffer (up to 3,123 bytes for a 100×50 image with 10-bit color and 8-bit alpha). A crafted HEIF file can exploit…
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Appears with

ai model Claude Opus 4.8 1ai model Claude Opus 5 1organization Bugcrowd 1organization Hacktron 1product Claude Opus 4.8 1product Claude Opus 5 1product libheif 1vendor Anthropic 1vendor Debian 1vendor Discourse 1vendor ImageMagick 1vendor OpenAI 1victim OpenAI 1
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