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In an anonymous post on an internet forum, we got the first warning about what some are calling one of the most serious families of software vulnerabilities ever discovered. AIs helped find them. Here’s what happened, why, and how it fits into the bigger picture. Thread 🧵

Hours later, the PHP Foundation announced that two critical vulnerabilities had been discovered in PHP, a programming language used in an estimated 70% of websites worldwide. It said an emergency security upgrade wouldn’t be available until the next day.

On Wednesday we learned the full seriousness of the problem: these bugs put any server running PHP at risk of being hacked. That’s huge swathes of the internet. For example, an estimated 40% of websites use WordPress, due to its ease of use, and it relies on PHP.

Already government websites, including those of the United Kingdom, the Netherlands, Germany, France, Belgium, Finland, Denmark, Czechia, Canada, Australia, and Japan, have had to be taken down as a preventative measure while their systems are patched.

To those paying close attention, this won’t be any surprise: AIs, including OpenAI’s GPT-5.6 Sol and Google’s Gemini 4 Argon, were used to help find these vulnerabilities.

In April of this year, AI company Anthropic announced its then-new Mythos AI, which it deemed too dangerous to release due to its advanced cyberoffensive capabilities. Mythos has since found over 33,000 high- or critical-severity vulnerabilities in computer systems.