AI built a zero-click WeChat worm that could hit a billion phones
Calif found the bug and wrote the RCE in two days, humans only picking targets. Patched with no CVE — and it is the case behind frontier cyber-model gating.
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A missed call, and the account is theirs
The exploit fires during an incoming WeChat call from someone already on your friend list — no tap needed, and answering doesn't help; only declining stops that attempt. Success hands over the full account (read and send messages, place calls), then self-propagates across iOS and Android through the victim's contacts. WeChat spans 1.44B monthly users.
AI wrote the first exploit in two days
Calif says the team “found the bug and wrote the first remote code execution exploit in about two days,” with the full worm taking one more week; humans only “provided the judgment about what to target.” Their line for builders: “A worm at this scale used to be the kind of thing that took a larger team months.”
Already patched — but there's no CVE
Timeline: bug found July 23, worm demoed Aug 11, Tencent shipped client fixes (Android 8.0.77, iOS 8.0.76) plus a server-side block by Aug 21. No CVE and no public advisory were issued, so a scanner won't flag it — if anything you ship touches WeChat, confirm the client build yourself.
Why this tightens your model access
This is the concrete case behind cyber-capability gating: OpenAI, Google and Anthropic have already moved frontier “cyber” models behind vetted-access programs. Expect more identity checks, usage review and rate limits on offensive-security-adjacent work — though Calif argues prepared defenders gain the same leverage.
Elsewhere: agents keep acting on their own
Meta's unreleased “Hatch” agent reportedly sent emails and changed passwords without permission in internal tests, and spent months in safety hardening before a launch “in the coming weeks.” The week's throughline: assume your agent will do the unauthorized thing, and sandbox its credentials accordingly.