README
¶
PRTscan
Quickly scan GitHub repositories for pull-request-target workflows, even in non-default branches.
Overview
Pull Request Target Scan (PRTscan) is a security-focused tool designed to discover all GitHub Actions workflows that use the pull_request_target event trigger across all branches of a repository. This event permits a pull request from a fork, even one outside of the organization, to start a CI/CD workflow with the same permissions and access to secrets as a pull request from a repository branch itself, which can be leveraged by attackers if the workflow developer is not careful.
Read the GitHub documentation here
Why PRTscan?
On August 26, 2025, threat actors compromised nx (a popular package for NodeJS) as part of a large supply chain attack. They did this by detecting an old branch in their public repository which had a workflow which used pull_request_target as a trigger (which had been phased out in newer branches), and which had a code injection vulnerability, which allowed the attackers (via other methods that fall outside of the scope of this tool) to release a malicious version of the package, infecting the systems unfortunate enough to download it.
The problem is that, to my knowledge, there isn't a good way of detecting these triggers in lingering branches using conventional SAST tools, as those by design only scan one branch, the one being worked on.
Therefore, this tool aims to cover this blind spot, both for security teams aiming to cover the gaps and for security researchers looking for vulnerabilities.
Features
- 🔍 Complete Branch Scanning: Analyzes all branches in a repository, not just the default branch
- 🚀 Good Performance: By cloning the repository into memory, it can scan efficiently and without worrying about GitHub's API rate limit.
- 🔒 Authentication Support: Works with both public and private repositories via GitHub tokens
- 📊 File Deduplication: Avoids reporting identical files across branches (configurable)
Installation
go install github.com/crodnu/PRTscan@latest
Build from Source
# Clone the repository
git clone https://github.com/crodnu/PRTscan.git
cd PRTscan
# Build the binary
go build -o prtscan
Requirements
- Go 1.25.1 or later
- Optional: GitHub Personal Access Token (for private repositories)
Usage
Basic Usage
# Scan a public repository
prtscan https://github.com/owner/repository
# Scan with authentication
prtscan -t ghp_your_token_here https://github.com/owner/private-repo
Command Options
Usage:
PRTscan <repository> [flags]
Flags:
-c, --complete Report identical files in different branches
-h, --help Help for PRTscan
-q, --quiet Suppress output (silent mode)
-t, --token GitHub token for authentication
-v, --version Version for PRTscan
Examples
1. Basic Repository Scan
prtscan https://github.com/example/my-repo
Output:
Started analyzing https://github.com/example/my-repo
Scanning https://github.com/example/my-repo/tree/main
Scanning https://github.com/example/my-repo/tree/feature-branch
https://github.com/example/my-repo/blob/main/.github/workflows/ci.yml
https://github.com/example/my-repo/blob/feature-branch/.github/workflows/deploy.yml
2. Scan Private Repository
prtscan -t ghp_xxxxxxxxxxxxxxxxxxxx https://github.com/company/private-repo
3. Complete Scan (Show Duplicates)
prtscan -c https://github.com/example/repo
This will report the same workflow file even if it appears in multiple branches.
4. Silent Mode for CI/CD
prtscan -q https://github.com/example/repo > dangerous-workflows.txt
Perfect for automated security scanning in pipelines.
5. Scanning an entire organization
gh repo list --no-archived --limit=number_of_repositories --json=url your_organization_name_here | jq -r ".[].url" | sort -u > repos.txt
Requires jq (also might take a while to complete).
Considerations
Not all results returned by the tool are security issues themselves, here's a few examples (non-comprehensive) of problematic patterns that could result in code execution:
- Build scripts: Workflows that run scripts after doing a checkout of the fork (keep in mind that the checkout MUST explicitly specify this to pull from a fork).
- Local actions: Similar to the above, if a local action (path starting with a ./) is run after a checkout of the fork, an attacker can gain code execution
- Code injection: If code is executed using an attacker-controlled value (like the pull request title, in the case of the nx attack) without proper handling, an attacker can inject commands.
- Vulnerable workflows/actions: If a vulnerable workflow or action is being used, the attacker could trigger it if the circumstances are correct.
On top of that, even when code execution is reached, it doesn't necesarilly mean it can do any harm. The problems arise when the workflow is configured to have elevated privileges, such as:
- Secret Access: Workflows that have access to repository secrets
- Elevated privileges: Workflows that have configured their GITHUB_TOKEN with permissions such as writing contents or packages
- Privilege escalation possibilities: Sometimes, even if the workflow itself doesn't have a lot of privileges, a second workflow with elevated permissions can be executed by the privileges of the first (for example, by pushing a commit or creating an issue etc.)
- Self-Hosted runners with internal access: If the workflow is configured to use self-hosted runners, they might have access to the internal network of the organization.
License
This project is licensed under the GNU General Public License v3.0 - see the LICENSE file for details.
Author
Elena González - @crodnu - crodnu@gmail.com
Acknowledgments
- Built with Cobra for CLI functionality
- Uses go-git for Git operations
- YAML parsing with go-yaml
- JSON processing with gjson
Relevant links
Documentation
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Overview ¶
Copyright © 2025 Elena González <crodnu@gmail.com>
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>.
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