XBOW, the Seattle-based autonomous offensive security company, earned Google's first $250,000 full-chain Chrome reward under the Chrome Vulnerability Reward Program's 2026 rules after one researcher and AI agents running OpenAI's GPT-5.6 Sol chained three previously unknown bugs into a single exploit that ran code on a Windows machine when a user loaded a web page1,2,4. The six-day campaign cost roughly $40,000 in API compute charges3.
XBOW disclosed the work on October 13, 2026. The company built the exploit between August 2 and August 7, during the Black Hat and DEF CON conferences in Las Vegas. Google has since confirmed all three bugs, shipped fixes, and paid the bounty.
Three bugs, two sandboxes
Chrome runs web-page code inside two nested sandboxes. The chain crossed both. The first flaw sat in V8, Chrome's JavaScript engine: a bug in the Maglev compiler let separate JavaScript objects share a mutable number during deoptimization, giving the attacker control of memory inside V8's protected region. The second flaw, in Chrome's animated WebP decoder, used that control to break out of the engine's inner sandbox and make one precise write to the computer's memory. A third bug in Crashpad (CVE-2026-78952) turned that single write into full code execution outside the browser. The result: malware, ransomware, or credential theft with no click or download required.
Before the fixes, XBOW estimated the class of flaw sat in the path of roughly one billion people running Chrome on Windows globally5. None of the three vulnerabilities were ever exploited against real users. The two bugs carrying public identifiers were patched in Chrome 152.0.7977.65 on August 25 and 152.0.7977.82 on September 3.
Human-agent division of labor
XBOW's own account describes the AI agents searching Chrome's source code, testing ideas, building proofs of concept, and writing first drafts of the exploit. The human researchers chose targets, supplied context, challenged the agents' outputs, and decided which pieces to stitch together. The chain nearly failed when one bug turned out to be already known to Google; XBOW had built the exploit in swappable parts with backups ready, replaced the component, and the chain held.
Oege de Moor, XBOW's founder, said it took an estimated $40,000 of compute and six days for a single researcher to produce a chain that previously would have taken months. XBOW's first full Chrome chain had taken two months to complete. The Chrome Vulnerability Reward Program awards at most four full-chain exploits a year.
ANALYSIS The cost ratio is the sharpest data point: $40,000 in compute yielded a $250,000 bounty, a 6:1 return before labor, compressing a timeline that XBOW itself previously measured in months down to under a week. The episode also marks the first time an autonomous security platform has collected a top-tier Chrome bounty, establishing a concrete precedent for AI-augmented vulnerability research at production scale.