Your Commit Metadata Is Lying: VS Code Contamination and the Collapse of Code Provenance
The Finding
The artifact is a 'Co-Authored-by Copilot' trailer that Microsoft's VS Code is writing into git commits from developers who never turned on AI assistance. Publicly: the unauthorized trailer is appearing in production commits. Not publicly confirmed: the affected version range, the total scope, or whether the fix has shipped. The trailer sits under the developer's commit signature either way. Signed commits are now attesting to authorship claims the signer did not make.
This is not a telemetry story. It is a supply-chain integrity story. Any pipeline that trusts commit metadata for provenance — SLSA attestations, SOC 2 SDLC evidence, regulated-code policies, IP ownership determinations — is running on contaminated data for the affected window.
The Broader Pattern: AI Code Is the Majority, and Controls Haven't Caught Up
The VS Code contamination lands next to two related data points. Airbnb disclosed that 60% of new code is now AI-generated. Treat that as the industry floor, not the ceiling. Separately, widely-read tutorials now walk non-developers through standing up full OAuth-connected Gmail clients in a weekend using Codex, with gmail.modify scopes cached in local SQLite on unmanaged hardware.
Research also put a number on the drafting side: LLMs corrupt approximately 25% of document content in long editing workflows. That finding extends to any GRC, legal, or compliance pipeline using AI-assisted drafting.
The signature on the commit covers the metadata the committer did not author. That is a supply-chain question, not a telemetry question.
Cross-Source Analysis
Three independent sources point the same direction: the provenance assumptions that held in 2022 no longer hold. VS Code contaminates metadata silently. AI agents let any employee stand up an unsanctioned OAuth client against corporate SaaS. The share of AI-authored code reaching production has crossed the majority line. Detection engineering should now treat AI-authored commits as the common case, not the exception.
| Surface | Control Assumed | What Broke | Detection Signal |
|---|---|---|---|
| VS Code commits | Metadata = actual authorship | Silent injection of AI attribution | Grep for 'Co-Authored-by: Copilot' in regulated repos |
| OAuth-connected shadow clients | DLP covers all mail egress | Local SQLite cache on personal device | New client IDs with gmail.modify in Workspace audit |
| AI-generated dependencies | Package names are human-vetted | Hallucinated packages = slopsquatting targets | First-seen packages on AI-authored PRs |
What to do
Grep all regulated repos for 'Co-Authored-by: Copilot' and variants today; document scope and notify Legal and GRC
Open a vendor-risk ticket with Microsoft requiring written confirmation of affected VS Code versions, root cause, and remediation timeline
Audit Google Workspace and Entra ID OAuth grants for non-Marketplace apps with mail.* or drive.* scopes granted in the last 90 days; revoke unauthorized grants
Add AGENTS.md, .codex/, .factory/, .cursorrules to secret-scanning and pre-commit hook coverage by end of sprint
Publish AI-assisted code policy requiring commit tags, mandatory SCA on AI-authored PRs, and ban on auto-installing AI-suggested packages from uncurated registries