Starting June 18, 2026, actions/checkout v7 will refuse to fetch code from forked pull requests in pull_request_target and workflow_run events by default, blocking common pwn request attack patterns. This update prevents untrusted fork code from running with full workflow privileges, and applies to all maintained versions by July 16, 2026, unless the “allow-unsafe-pr-checkout” flag is set.

• Starting June 18, 2026, actions/checkout v7 blocks fetching forked PR code in pull_request_target/workflow_run by default, requiring an explicit "allow-unsafe-pr-checkout" opt-in; full rollout across maintained versions completes by July 16, 2026.
• This directly targets "pwn request" attacks where a malicious fork PR exploits pull_request_target's full GITHUB_TOKEN access and secrets to steal credentials or push malicious code.
• Real-world incidents like the s1ngularity Nx package hijack and attacks on PostHog, TanStack, and kubernetes-el prompted the fix.
• The fix only closes the actions/checkout vector—untrusted code can still slip in via git, GitHub CLI, or other triggers, so teams still need to minimize pull_request_target use, restrict permissions, and validate inputs.