XBOW used GPT-5.6 Sol to build a $250,000 Chrome exploit in six days

What happened

Security company XBOW has won $250,000 from Google’s Chrome bug bounty programme, XBOW said on 13 October. XBOW says it is the first full-chain Chrome award under rules Google introduced in April 2026. Google is an Internet and software company based in Mountain View.

Six days and $40,000 Dolan-Gavitt and the agents built the awarded chain between 2 and 7 August, while the team was in Las Vegas for Black Hat and DEF CON. Data and security XBOW used GPT-5 (large language model by OpenAI).6 Sol to build a $250,000 Chrome exploit in six days The Chrome exploit cost about $40,000 in compute and chained three bugs Google has now fixed.

XBOW’s team had spent two months on a first attempt that collided with a bug Google already knew. It built the exploit with AI agents (AI that carries out multi-step tasks rather than answering one question) running OpenAI’s GPT-5.6 Sol.

The attack chained three unknown Chrome bugs. Loading a web page was enough to run code outside Chrome’s sandbox on a Windows computer, with no click or download.

Google has fixed all three bugs, and XBOW says they were never used against Chrome users. Before the fixes, the bugs exposed about one billion people running Chrome on Windows, by the company’s estimate.

XBOW puts the compute cost at about $40,000, based on its usage logs. Founder and CEO Oege de Moor wrote that the company chose a model available to anyone on purpose.