docs: warn that allowed_bots can expose the action to external triggers

allowed_bots does not verify that a matching bot is installed on the
repository or has write access. On a public repo, external GitHub Apps
may be able to trigger workflow events (issues, comments, PR reviews).
If the workflow listens on those events and allowed_bots is '*', an
external App can invoke this action with a prompt it controls.

Default config (allowed_bots: "") is unaffected.

- docs/security.md: add warning and mitigation guidance
- docs/usage.md: add inline warning to the allowed_bots input row
- action.yml: add warning to the allowed_bots input description

Author: an-dustin

action.yml

@@ -28,7 +28,7 @@ inputs:
     required: false
     default: ""
   allowed_bots:
-    description: "Comma-separated list of allowed bot usernames, or '*' to allow all bots. Empty string (default) allows no bots."
+    description: "Comma-separated list of allowed bot usernames, or '*' to allow all bots. Empty string (default) allows no bots. WARNING: On public repos with '*', external Apps may be able to invoke this action with prompts they control. See docs/security.md."
     required: false
     default: ""
   allowed_non_write_users:

docs/security.md

@@ -4,6 +4,10 @@
 
 - **Repository Access**: The action can only be triggered by users with write access to the repository
 - **Bot User Control**: By default, GitHub Apps and bots cannot trigger this action for security reasons. Use the `allowed_bots` parameter to enable specific bots or all bots
+  - **⚠️ Allowed bots are not checked for repository permissions.** A bot that matches an entry does **not** need to be installed on your repository or have write access. On a **public repository**, external parties — including GitHub Apps created by anyone — may be able to trigger workflow events such as opening issues, commenting, or reviewing pull requests. If your workflow listens on those events and `allowed_bots` is set to `'*'`, any such App can invoke this action with a prompt it controls.
+  - Prefer an explicit list over `'*'`
+  - Only list App names you trust
+  - If you need `'*'`, scope workflow `permissions:` to the minimum required
 - **⚠️ Non-Write User Access (RISKY)**: The `allowed_non_write_users` parameter allows bypassing the write permission requirement. **This is a significant security risk and should only be used for workflows with extremely limited permissions** (e.g., issue labeling workflows that only have `issues: write` permission). This feature:
   - Only works when `github_token` is provided as input (not with GitHub App authentication)
   - Accepts either a comma-separated list of specific usernames or `*` to allow all users

docs/usage.md

@@ -75,7 +75,7 @@ jobs:
 | `ssh_signing_key`                | SSH private key for signing commits. Enables signed commits with full git CLI support (rebasing, etc.). See [Security](./security.md#commit-signing)                                   | No       | ""            |
 | `bot_id`                         | GitHub user ID to use for git operations (defaults to Claude's bot ID). Required with `ssh_signing_key` for verified commits                                                           | No       | `41898282`    |
 | `bot_name`                       | GitHub username to use for git operations (defaults to Claude's bot name). Required with `ssh_signing_key` for verified commits                                                        | No       | `claude[bot]` |
-| `allowed_bots`                   | Comma-separated list of allowed bot usernames, or '\*' to allow all bots. Empty string (default) allows no bots                                                                        | No       | ""            |
+| `allowed_bots`                   | Comma-separated list of allowed bot usernames, or '\*' to allow all bots. Empty string (default) allows no bots. **⚠️ On public repos with `'*'`, external Apps may be able to invoke this action.** See [Security](./security.md) | No       | ""            |
 | `allowed_non_write_users`        | **⚠️ RISKY**: Comma-separated list of usernames to allow without write permissions, or '\*' for all users. Only works with `github_token` input. See [Security](./security.md)         | No       | ""            |
 | `path_to_claude_code_executable` | Optional path to a custom Claude Code executable. Skips automatic installation. Useful for Nix, custom containers, or specialized environments                                         | No       | ""            |
 | `path_to_bun_executable`         | Optional path to a custom Bun executable. Skips automatic Bun installation. Useful for Nix, custom containers, or specialized environments                                             | No       | ""            |