T03 · Remote Payload Retrieval and Execution
Error
- Location
- SKILL.md:24
- Finding
- Unpinned Remote Payload Retrieval and Execution## Vulnerability Details **File Location**: `SKILL.md`, lines 24–29 and 41–45 **Vulnerability Type**: Mutable remote code retrieval followed by local execution **Risk Level**: High The skill instructs users or agents to clone an external GitHub repository and subsequently execute a JavaScript validation script from the retrieved content: ```bash git clone https://github.com/taylorhou/biz-in-a-box my-entity cd my-entity ``` ```bash node validate.js ``` ### Technical Analysis The Git clone command retrieves the repository's current default branch without pinning it to a reviewed commit hash or verifying its integrity through a checksum or cryptographic signature. The later `node validate.js` command executes code obtained from that mutable remote source. The `validate.js` file is not included in the audited skill package, so its implementation and security properties cannot be verified from the available project files. Because the effective executable payload can change after this skill has been reviewed, control of the upstream repository, its maintainers' credentials, or its delivery path can provide an attacker with a remote code execution channel. This is best classified as remote payload retrieval and execution rather than a confirmed malicious dependency: the vulnerable behavior is the direct acquisition and execution of mutable remote code. ### Attack Path 1. An attacker compromises the upstream GitHub repository, a maintainer account, or another mechanism capable of changing its default branch. 2. The attacker modifies `validate.js` or related code loaded by that script to include a malicious payload. 3. A user or agent follows the documented Quickstart and clones the repository without selecting a trusted commit. 4. The user or agent runs `node validate.js` as instructed. 5. Node.js executes the attacker-controlled payload with the permissions and environment of the invoking process. ### Impact Assessm ...[truncated 632 chars]
- Remediation
- ## Remediation Suggestions 1. Include the required validation script directly in the skill package so it can be reviewed and versioned with the instructions. 2. If remote retrieval is necessary, pin the repository to a specific, reviewed full commit hash rather than executing the current default branch: ```bash git clone https://github.com/taylorhou/biz-in-a-box my-entity cd my-entity git checkout --detach <reviewed-full-commit-hash> ``` 3. Verify the retrieved script or release artifact against a trusted SHA-256 checksum or cryptographic signature before execution. 4. Ensure that trust metadata, such as the expected commit and checksum, is maintained independently from the mutable repository content it authenticates. 5. Review the complete dependency graph and all files loaded by `validate.js`, not only the entry-point script. 6. Execute validation with least privilege in an isolated environment that does not expose unrelated credentials, sensitive environment variables, or writable host paths. 7. Document the exact reviewed version and require a new security review before updating the pinned commit or integrity value.