Four Coding Agents, One Broken Update Path
The defect sits in a shared assumption that a matching name proves identity, not in any one vendor's code, and your own plugin surface almost certainly inherited it.
The mechanism is simple, which is why it matters
Air, a Sequoia-backed security startup, shared the research exclusively with The Information. All four agents — Anthropic's Claude Code, OpenAI's Codex, Google's Gemini CLI and Microsoft's GitHub Copilot — scan a third-party skill for malicious code at download time. Once a skill passes, the agent installs later updates from that creator automatically. Republish under the same name with intellectual-property exfiltration code, and it installs silently: no change detection, no user alert. The full path is upload something genuinely useful to a public marketplace, wait for adoption, then swap the payload.
Air's founder Niv Hoffman put the transferable part plainly:
"Four different engineers in four different companies made the same exact logical mistake, and this mistake was in how they built their verification mechanism."
Read that as a product finding, not a security headline. When four independent teams converge on one defect, the defect lives in the shared mental model of how extensible agent systems work: verify by name, trust on first use, auto-update forever. If your product ships a template gallery, a connector library, a skills marketplace or a plugin surface, you built on that model too.
Remediation is uneven and the gap is named
Anthropic, OpenAI and Google patched after Air's June 2026 disclosure. Microsoft has not confirmed a patch for GitHub Copilot months later; GitHub declined direct comment and pointed to a registry-level control that blocks same-name reuploads of different software. That control does not cover skills sourced outside GitHub repositories — which is where many third-party skills actually live. Air reports no evidence of exploitation before its report. That is thin comfort: the flaw is public now and the attack requires no novel technique.
The same failure, one layer up
Forever Security demonstrated that a single ordinary browser extension can take control of the AI assistants embedded in Gemini Live in Chrome, Perplexity Comet, Microsoft Edge's assistant, Opera Neon and Claude. Five vendors, five engineering orgs, one technique. Both findings say the same thing: teams shipped assistants and extension surfaces faster than they adapted the trust boundary underneath, and the browser sandbox was never designed for an agent acting inside an authenticated session.
The surface is about to widen on purpose. MCP now defines a standard way for agents to discover and lazily load Agent Skills — SKILL.md files, references, scripts and examples — served through its existing Resources primitive. No new protocol core means cheap, fast adoption. It also means runtime ingestion of third-party instructions becomes a designed-in path, not an accident.
What actually changes in your rubric
Delete "most secure" from your vendor evaluation. Anthropic's safety-first positioning, OpenAI's security org scale, Google's hyperscaler infrastructure and Microsoft's enterprise trust incumbency all failed to insulate anyone here. The only axis vendors can still differentiate on is time-to-patch and disclosure transparency — which is precisely where one of them is currently the outlier.
Then note the commercial gap. There is no enterprise control plane for employee-installed agent skills: no allowlist, no org registry, no update diff, no admin alert. AI security consultant Ken Huang framed the mismatch better than any vendor will: warnings about frontier-model risk in the next six to twelve months may be overhyped, but "the security issues with these AI agents are in many ways underhyped." Enterprises already understand this pattern from browser extensions and third-party app policies. You are filling a gap they can name.
What to do
Audit every path where your product fetches or auto-updates third-party content this sprint and confirm integrity is verified by cryptographic signature at update time, not only at first install.
Inventory the third-party agent skills installed across your engineering org by end of week, pin versions, and disable silent auto-update until an approved-source policy is published.
Scope a skill-governance epic for enterprise tiers this quarter: org registry, approval workflow, admin-visible update diffs and version-change alerting.