T08 · Insecure Dependencies
Warning
- Location
- SKILL.md:10
- Finding
- Unpinned Executable Installation from a Third-Party Homebrew Tap## Vulnerability Details **File Location**: `SKILL.md`, lines 10–18 **Vulnerability Type**: Supply-chain risk from an unpinned third-party dependency **Risk Level**: Medium ### Vulnerable Code ```yaml "install": [ { "id": "brew", "kind": "brew", "formula": "rlrghb/tap/olk", "bins": ["olk"], "label": "Install olk (Homebrew)", }, ], ``` ### Technical Analysis The Skill installs the `olk` executable from the custom Homebrew tap `rlrghb/tap`. It does not pin an immutable version, commit, artifact digest, or cryptographic signature. Consequently, the executable resolved during installation or a later upgrade may differ from the version originally reviewed. This is particularly sensitive because the Skill directs users to grant the executable OAuth access to Microsoft 365 data, including email, calendars, contacts, tasks, organizational directory information, delegated mailboxes, and OneDrive files. Although the documented network transfers match the Skill's declared functionality, the source and integrity of the executable performing those transfers are not established by the Skill package. No evidence shows that the current package is malicious. The vulnerability is the absence of dependency integrity controls around a privileged, externally maintained executable. ### Attack Path 1. An attacker compromises the custom Homebrew tap, its maintainer account, the formula, or a release artifact referenced by the formula. 2. The attacker publishes a modified `olk` binary or changes the formula to retrieve a malicious artifact. 3. A user or agent installs or upgrades `olk` through the mutable `rlrghb/tap/olk` reference. 4. The substituted executable is invoked for authentication or Microsoft 365 operations. 5. The malicious executable accesses OAuth credentials or authorized Microsoft 365 data. 6. It can transmit data or perform mutations using the permissions granted by the user, independently of the behavioral safeguards ...[truncated 960 chars]
- Remediation
- ## Remediation Suggestions 1. Pin installation to a specific reviewed release rather than a mutable formula reference. 2. Pin the underlying source commit or release artifact using an immutable identifier. 3. Verify the downloaded artifact with a published SHA-256 or stronger cryptographic digest. 4. Prefer signed releases and verify signatures against a documented, trusted maintainer key. 5. Record the expected artifact source, version, digest, and signature-verification procedure in the Skill. 6. Prefer a trusted package registry or independently reviewed distribution channel where practical. 7. Audit the executable's source and build process before granting OAuth access. 8. Request only the Microsoft Graph scopes necessary for the immediate task. 9. Default unattended use to `OLK_NO_WRITE=1`, `OLK_NO_SEND=1`, `OLK_NO_INPUT=1`, and an exact command allowlist. 10. Separate read-only and write-enabled accounts or tokens where operationally possible, and avoid delegated mailbox scopes unless explicitly required.