CVE-2023-52137 (YAML, published 2023-12-29T17:16Z)
Description: value: The [`tj-actions/verify-changed-files`](https://github.com/tj-actions/verify-changed-files) action allows for command injection in changed filenames, allowing an attacker to execute arbitrary code and potentially leak secrets. The [`verify-changed-files`](https://github.com/tj-actions/verify-changed-files) workflow returns the list of files changed within a workflow execution. This could potentially allow filenames that contain special characters such as `;` which can be used by an attacker to take over the [GitHub Runner](https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners) if the output value is used in a raw fashion (thus being directly replaced before execution) inside a `run` block. By running custom commands, an attacker may be able to steal secrets such as `GITHUB_TOKEN` if triggered on other events than `pull_request`.

This has been patched in versions [17](https://github.com/tj-actions/verify-changed-files/releases/tag/v17) and [17.0.0](https://github.com/tj-actions/verify-changed-files/releases/tag/v17.0.0) by enabling `safe_output` by default and returning filename paths escaping special characters for bash environments.
Severity: nan (CVSS v3 base score: 8.8)
Weakness: CWE-77 \u2014 Improper Neutralization of Special Elements used in a Command ('Command Injection')
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
Repository: https://github.com/tj-actions/verify-changed-files
Files changed:
README.md
action.yml
entrypoint.sh
Commit message: Merge pull request from GHSA-ghm2-rq8q-wrhc

* feat: add `safe_output` input enabled by default

* fix: migrate README to safe uses of interpolation

* fix: also sanitize `)`

* fix: remove sanitization of `'`

* fix: also sanitize `|`

* fix: also sanitize `&`

* fix: also sanitize `;`

Vulnerable code:
          echo "Changed files: ${{ steps.verify-changed-files.outputs.changed_files }}"
          echo "Changed files: ${{ steps.verify-changed-files.outputs.changed_files }}"

Fixed code:
          safe_output: false # true by default, set to false because we are using an environment variable to store the output and avoid command injection.
        env:
          FILES_CHANGED: |-
            ${{ steps.verify-changed-files.outputs.changed_files }}
          echo "Changed files: $FILES_CHANGED"
          safe_output: false
        with:
          safe_output: false
        env:
          FILES_CHANGED: |-
            ${{ steps.verify-changed-files.outputs.changed_files }}
          echo "Changed files: $FILES_CHANGED"
  safe_output:
    description: "Apply sanitization to output filenames before being set as output."
    required: false
    default: "true"
        INPUT_SAFE_OUTPUT: ${{ inputs.safe_output }}
  if [[ "$INPUT_SAFE_OUTPUT" == "true" ]]; then
    CHANGED_FILES=${CHANGED_FILES//$/\\$} # Replace $ with \$
    CHANGED_FILES=${CHANGED_FILES//\(/\\\(}} # Replace ( with \(
    CHANGED_FILES=${CHANGED_FILES//\)/\\\)}} # Replace ) with \)
    CHANGED_FILES=${CHANGED_FILES//\`/\\\`} # Replace ` with \`
    CHANGED_FILES=${CHANGED_FILES//|/\\|} # Replace | with \|
    CHANGED_FILES=${CHANGED_FILES//&/\\&} # Replace & with \&
    CHANGED_FILES=${CHANGED_FILES//;/\\;} # Replace ; with \;
  fi