Your organisation's browser origin allowlist holds one entry, your internal documentation host. Mid-task the agent clicks a link on that host pointing at an external vendor site, and the page loads. Your compliance owner files it as a product defect and asks you to confirm. How should you characterise what happened?

Hardcursorbrowserallowlistsecurity

Last reviewed 21 Aug 2026

The allowlist restricts automatic agent navigation but cannot prevent every navigation path, so a link followed off an allowed origin is documented behaviour rather than a defect to file.Correct answer
The allowlist is an egress boundary for the agent, so arriving on a non-allowed origin can only mean the entry was written wrongly or the dashboard change was not saved for the organisation.
The allowlist governs only where MCP tools may execute rather than which pages load, so the click fell outside its scope and a separate navigation policy would have to be added alongside it.
Once the browser sits on a non-allowed origin the tools carry on working as normal, so the load is harmless in itself and the list only ever gates the first navigation of a session.

Show answer & explanation

Correct answer: A. The allowlist restricts automatic agent navigation but cannot prevent every navigation path, so a link followed off an allowed origin is documented behaviour rather than a defect to file.

Explanation

The principle — The origin allowlist restricts automatic agent navigation but cannot prevent all navigation paths. It is best-effort control over where the agent goes on its own, not a network egress boundary. The gaps are named in the documentation: a link clicked on an allowed domain that points elsewhere will load, a redirect from an allowed origin to a non-allowed one is permitted, and client-side navigation via script from an allowed origin succeeds too.

Why the key is correct — What happened is the first of those cases exactly. The agent began on an allowed origin, followed a link, and ended up somewhere the list does not name. No entry was wrong and nothing was unsaved. Filing it as a defect sends engineering hunting for a bug that does not exist, and it hides the action the incident actually calls for: reviewing which domains you allow, in the light of where they link and redirect. A documentation host full of outbound vendor links is a wide allowance dressed as a narrow one.

Why the others are wrong — Treating the allowlist as an egress boundary is the central error, because allowlists in firewalls and proxies do fail closed and the habit transfers. Restricting the list's meaning to MCP tool execution is half the truth — it does gate that, and it also gates which URLs the agent may navigate to automatically. And believing the constraint lapses once the browser has left an allowed origin gets a real protection backwards: on an origin outside the list, the browser tools are blocked, including when a person navigated there manually.

Remember this — Ask what an allowed domain can reach, not just what it is. Review the allowlist on a schedule, and weigh each entry by its outbound links and redirects, because those inherit the trust you granted the entry itself.

Sources — Cursor's Browser tool documentation.

Sources

Primary sourceBrowser — Cursor · accessed 19 Aug 2026
“The origin allowlist restricts automatic agent navigation but cannot prevent all navigation paths.”

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