Pin GitHub Actions to full-length commit SHAs

[Dan Fiedler (danfiedler-msft)]

Summary

This PR pins GitHub Actions to full-length commit SHAs for improved security and reproducibility and adds a 7 day cooldown to Dependabot configuration for GitHub Actions. This work is described in more detail at https://aka.ms/action-pinning.

Why?

Pinning actions to commit SHAs prevents supply-chain attacks where a tag could be moved to point to malicious code. This is a recommended security best practice per the GitHub Actions security hardening guide.

This change mitigates the risk of tag retargeting to malicious code as seen in incidents like the tj-actions/changed-files action compromise or codfish/semantic-release-action compromise and improves the integrity and reproducibility of the CI/CD pipeline.

What changed?

Action pinning: Third-party action references in .github/workflows/ that used mutable tag-based references (e.g., actions/checkout@v4) have been updated to full-length commit SHAs with a version comment (e.g., actions/checkout@<sha> # v4) using the pinact tool. References that were already pinned to a SHA, or that used immutable release tags, were left unchanged.

Dependabot configuration: .github/dependabot.yml has been updated to ensure a github-actions package-ecosystem section is present with a cooldown configuration (default-days: 7). If the file did not exist, it was created. If a github-actions section already existed, only the cooldown block was added or its default-days value was increased to 7 if it was lower. The 7-day cooldown provides a window for the community to detect and report compromised releases before they are automatically proposed as updates, reducing exposure to supply-chain attacks via newly published malicious versions.

Is this safe to merge?

Yes. The pinned SHAs correspond to the same commits that the existing tags pointed to. No behavioral changes in action execution are introduced. You can verify the pinned SHA value using the GitHub REST API (e.g., the commit hash for actions/checkout@v7 can be found in the sha property in the JSON response for GET https://api.github.com/repos/actions/checkout/commits/v7).

Additional Information

For more information, please see https://aka.ms/action-pinning

[Copilot]

Pull request overview

This PR hardens the repository’s CI/CD security posture by replacing mutable GitHub Action tag references with full-length commit SHA pins (improving supply-chain resilience and reproducibility) and adding a 7-day Dependabot cooldown for GitHub Actions updates.

Changes:

• Pinned third-party and first-party GitHub Actions in existing workflows to full-length commit SHAs with version comments.
• Added .github/dependabot.yml configuration to enable weekly GitHub Actions updates with a 7-day cooldown window.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/workflows/stale.yml	Pins actions/stale to a full commit SHA for all stale-related jobs.
.github/workflows/stale-assigned.yml	Pins actions/stale to a full commit SHA.
.github/workflows/lock.yml	Pins dessant/lock-threads to a full commit SHA.
.github/workflows/jekyll-gh-pages.yml	Pins checkout, setup-node, and GitHub Pages actions to full commit SHAs.
.github/workflows/delete-merged-branches.yml	Pins actions/checkout to a full commit SHA.
.github/workflows/codeql-analysis.yml	Pins checkout and github/codeql-action steps to full commit SHAs.
.github/workflows/ci.yml	Pins checkout and setup-node to full commit SHAs.
.github/dependabot.yml	Adds Dependabot config for GitHub Actions updates with a 7-day cooldown.

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