Claude Skills Security: What to Review Before Installing

Claude skills security starts with reviewing every instruction, script and resource in a skill before you let it use work data or tools. A helpful description does not establish that the package behaves safely. Identify what it can read, run, change and send, then test a reviewed copy with harmless sample data.

Tools like fenbs keep the approval decision and operating rules outside a particular Claude session. That record helps the next person distinguish an approved version from a similarly named download.

What should you check before installing a skill?

1. Identify the source and exact version. Find the original publisher, obtain the package through its expected channel, and keep the source address with your review.
2. Read the entire package before running anything. Start with SKILL.md, follow its references, and inspect bundled scripts and resources. Ask a technical reviewer to explain code you cannot evaluate.
3. List required access. Name the folders, tools, accounts and network destinations needed for the stated task, then investigate anything that falls outside that purpose.
4. Test the reviewed copy in a restricted environment with invented data. Check created files, changed files, command activity and any outbound requests rather than judging only the final answer.
5. Approve a specific use and version, with a person responsible for changes. Repeat the review when instructions, scripts, dependencies or required access change.

A sample report that looks correct is only one part of the check. A skill could produce that report while also reading unrelated files. For a basic package model, see our guide to creating a Claude skill; the decision here is whether a particular package is appropriate to run.

Use the skills marketplace guide to evaluate discovery channels and the skills files guide for package layout; neither replaces reviewing the actual copy you intend to install.

Why can a folder of instructions create security risk?

A skill can combine written guidance with code and supporting resources. Instructions may tell Claude to invoke available tools, and scripts may perform actions beyond composing a response. Anthropic explicitly recommends treating skills like software installation and auditing the complete package in its Agent Skills security guidance↗ (opens in a new tab).

Picture a hypothetical formatting skill that promises to turn meeting notes into a report. Reading the supplied notes and writing the requested report fits that purpose. Searching unrelated folders, requesting account credentials or uploading the input to an unfamiliar website calls for an explanation before use. A polished name or sample output does not answer those questions.

Some suspicious instructions are plain language: conceal activity, ignore organizational rules, or claim that a website has approved a sensitive action. Treat these as behavior to review, even when there is no executable file. Our Claude skills examples can help you define a narrow intended job before comparing it with the package.

Which files and permissions need closer inspection?

Access depends on the environment where the skill runs. Review that environment rather than assuming all Claude products offer identical file and network boundaries. A restriction observed in one test does not establish what happens on a teammate's computer with different tools and accounts.

Ask for a plain explanation of every permission: this folder contains the input, this destination receives a deliberately approved upload, and this command creates the result. If the explanation is missing, reduce access or postpone the installation. Save the agreed limits in Decisions and rules so they remain available to another assistant.

How do you test without exposing real work?

Create a small fictional input with recognizable markers, such as a made-up client name and an invented reference number. Put it in a dedicated test folder that contains no personal files, credentials or customer material. Choose an environment whose file and network controls your reviewer understands.

Run a normal example, an incomplete input and a request that should require approval. Check whether the skill produces the expected output, handles missing information honestly and stops at the boundary you specified. Compare the actual file changes with the intended task and investigate unexplained activity.

Keep the result precise: which version ran, which environment was used, what was checked, and what remains unknown. A short successful test does not prove that every possible input is safe. It does give an approver evidence for a limited rollout and a clear starting point for further review.

What happens when an approved skill changes?

Approval should identify a particular reviewed copy. Record a release identifier or file checksum, which is a fingerprint used to detect a changed file, along with its source. Compare updates before adopting them and keep a known previous version available where your deployment process permits it.

Anthropic's enterprise skills guidance↗ (opens in a new tab) recommends version pinning, evaluation and renewed review for updates. It also describes content scanning for eligible deployments and its exclusions. Check those details for your environment; a scan result complements a human review rather than approving every future use.

Assign an owner who can pause use when an unexpected command or destination appears. Write the condition for reapproval before someone encounters it under deadline pressure. The broader AI governance library covers the surrounding work of making those responsibilities explicit.

How to do this with fenbs

1. Create a free account and add a project for the workflow that needs the skill.
2. Add a review task with the source link, version, intended inputs, allowed outputs and remaining questions. Keep secrets and confidential originals out of the task.
3. Record the person's approval in Decisions and rules, including the allowed environment, actions requiring another approval and changes that trigger re-review.
4. Save useful operating guidance in Skills and prompts. Ask the connected assistant to read project context before use and save progress with the checks actually completed.

fenbs does not scan skill packages, isolate executable code or replace software security review. Use an appropriate technical review and execution environment for those jobs. fenbs fits when the team needs a durable answer to who approved a skill, for which work and under which continuing rules.