Pin GitHub Actions to full-length commit SHAs

[Microsoft Open Source Security Bot (OssSecurityBot)]

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.

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). This groups Dependabot PRs for GitHub Actions and enforces a minimum 7-day cooldown between updates. 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 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).

---

_{For more information, visit https://aka.ms/action-pinning}

[mu-automation]

⏩ QEMU Validation Skipped

The PR was merged before validation completed.

This comment was automatically generated by the Mu QEMU PR Validation workflow.

[Michael Kubacki (makubacki)]

I'm going to drop the dependabot.yml update entirely since (1) we already added a 7 day cooldown for actions (the conflict) and (2) it changes line endings from CRLF -> LF. Please wait for that push.

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (release/202511@ba613ee). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release/202511     #932   +/-   ##
=================================================
  Coverage                  ?   10.20%           
=================================================
  Files                     ?      150           
  Lines                     ?    24583           
  Branches                  ?     2346           
=================================================
  Hits                      ?     2509           
  Misses                    ?    22038           
  Partials                  ?       36           

Flag	Coverage Δ
AdvLoggerPkg	3.02% <ø> (?)
HidPkg	2.79% <ø> (?)
MfciPkg	34.00% <ø> (?)
MsCorePkg	1.30% <ø> (?)
MsWheaPkg	7.37% <ø> (?)
XmlSupportPkg	25.46% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.