## Why
A user pointed out that the README pull request example interpolated
`${{ github.event.pull_request.base.ref }}` directly into a shell
command. GitHub Actions expands `${{ ... }}` expressions before the
shell runs, so copying that pattern into a workflow can let
attacker-controlled values such as branch names break shell syntax and
execute arbitrary commands.
This change hardens both the published examples and the composite action
itself so we are not shipping that pattern to users.
## What changed
- updated the README pull request review example to pass PR metadata
through `env:` and consume it as quoted shell variables
- added guidance to `docs/security.md` explaining why direct `${{ ...
}}` interpolation inside `run:` blocks is unsafe
- hardened `action.yml` so action inputs and step outputs are passed
into shell steps through environment variables instead of being spliced
directly into commands
- updated `examples/test-sandbox-protections.yml` to use the same safe
pattern
## Verification
- re-scanned this repository for attacker-controlled GitHub expressions
or action inputs interpolated directly into `run:` blocks
- parsed `action.yml` and `examples/test-sandbox-protections.yml` with
`Ruby` `YAML.load_file` to confirm the edited workflow files still parse
Michael Bolin
39b483218f