Fix GitHub Actions script injection RCE in sanitize.yml

[Copilot]

The changelog-format job interpolates changelog-reader-action outputs directly into a shell run: block via ${{ }}. The changes output contains arbitrary multi-line markdown from CHANGELOG.md, which is attacker-controlled on pull_request triggers. An attacker can terminate the cat << 'EOF' heredoc early and inject shell commands.

Vulnerability

# BEFORE — changes output is expanded inline before shell execution
run: |
    cat << 'EOF'
    ${{ steps.changelog_reader.outputs.changes }}
    EOF

A crafted CHANGELOG entry with EOF on its own line breaks the heredoc, and subsequent lines execute as shell commands on the runner.

Fix

• .github/workflows/sanitize.yml: Move ${{ }} expressions from run: to env: block so values are passed as data, not code

# AFTER — values passed as environment variables
env:
  CL_CHANGES: ${{ steps.changelog_reader.outputs.changes }}
run: |
    echo "${CL_CHANGES}"

Exploitability analysis

Only the changes output is exploitable. version is constrained to /[a-zA-Z0-9.\-+]+/ by the action's parser, and status is one of four hardcoded strings.

POC

• poc/poc.sh — simulates the vulnerable and fixed workflow steps locally, confirming RCE in the original and safe handling in the fix
• poc/malicious_changelog.md — example payload
• poc/README.md — full writeup