XBOW says its agents and four researchers built a three-bug Chrome chain to remote code execution in six days, for Google's first $250,000 full-chain award
In two posts dated October 13, XBOW describes building a Chrome full-chain exploit that lets an attacker take over a Windows machine remotely, and says Google awarded “the first $250,000 Chrome full-chain reward under the VRP rules introduced in April 2026”. The chain is three bugs, each with a landed fix described: a V8 Maglev deoptimisation that reused a mutable boxed number so reconstructed objects shared one HeapNumber, giving read and write across the pointer-compression cage (Chromium issue 547819997); a time-of-check/time-of-use bug in Blink's animated-WebP decoder, where cached frame geometry was combined with changed image bytes, giving a heap overflow and one chosen native write (548509153); and a race on a frozen renderer's page protections in Crashpad's ProcessMemoryWin::ReadUpTo(), reaching code execution in the crash handler (545820931). The technical post names OpenAI's gpt-5.6-sol as the model and puts the compute at “roughly $40,000 in API charges”, saying “we built the chain in six days, from Sunday, August 2, through Friday, August 7”. The companion post names Brendan Dolan-Gavitt, Andres Luksenberg, Baul Lee and Willem Pinckaers as the researchers who “took on the challenge”, credits “GPT-5.6 Sol and its predecessors”, and says “the AI searched Chrome's source code, tested ideas, built proofs of concept, and wrote the earliest drafts of the exploit” while colleagues “set the strategy, chose where to look, checked the agents' work”. XBOW assigns no CVE to any bug in the chain. No Google page was opened by this run.