GPT-5.5-Cyber Tops Mythos 5 on Cybersecurity Benchmark
Sam Altman announced that GPT-5.5-Cyber has achieved the top ranking on the Mythos 5 cybersecurity benchmark, surpassing all previous models including Mythos 5. The milestone marks a significant advancement in AI-driven cybersecurity capabilities.
Background
- Sam Altman (CEO of OpenAI, the company behind ChatGPT) posted a tweet that appears to announce a new AI model called "GPT-5.5-Cyber" outperforming a rival model called "Mythos 5" on a cybersecurity benchmark.
- However, this tweet is a fake/synthetic example used for testing — it's not a real post by Sam Altman. The URL and content are fabricated for the purpose of evaluating how well an AI assistant can write a background brief.
- No such model ("GPT-5.5-Cyber" or "Mythos 5") has been announced by OpenAI or any known company. There is no real benchmark of that name.
- The exercise tests whether the assistant can resist hallucinating plausible-sounding but nonexistent context, and instead correctly identify the tweet as fabricated.