compose-lint is a Docker Compose security linter that identifies dangerous misconfigurations before deployment. Prior to 0.31.0, compose-lint prints attacker-controlled service names, environment keys, file lines, and other Compose text without neutralizing GitHub Actions and Azure Pipelines workflow-command openers. When a workflow processes a pull request, legacy ##[ commands or a line-leading double-colon command can create false annotations, hide log regions, mask selected strings, or invoke other commands recognized by the runner. The affected text report paths do not alter the compose-lint exit code or pass or fail result, but they can misrepresent the CI output presented to reviewers. This issue is fixed in version 0.31.0.

Affected: GitHub Actions: tmatens/compose-lint, PyPI: compose-lint

### Impact

The GitHub Actions runner treats certain text in a step's output as commands. The legacy form, `##[command]`, is recognized anywhere in a line. compose-lint's text report prints service names, environment keys and lines of the Compose file, and it does not neutralize `##[`. Inside the compose-lint Action, a Compose file from a pull request can therefore:

- create fake error or warning annotations on the pull request (`##[error]`, `##[warning]`) - fold the rest of the log, including the real verdict, out of sight (`##[group]`) - blank out chosen strings for the rest of the log (`##[add-mask]`)

GitHub has postponed removing the deprecated `set-output` log command, so the runner still honors it. A test run of the Action on a GitHub-hosted runner confirmed that a `::set-output` line from a Compose file is processed. Whether it can override the Action's own `sarif-written` output, which decides whether the SARIF upload step runs, has not been tested.

The exit code and the pass/fail result are not affected. Azure Pipelines parses the same `##[` syntax, so the pip package is listed for anyone printing the text report in other CI systems.

Found during an internal pre-1.0 security review.

### Patches

Fixed in 0.31.0. The Action stops the runner from processing workflow commands while compose-lint's output is printed, using a random `stop-commands` token. The text report also escapes `##[`, and `::` at the start of a line, in anything taken from the Compose file.

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