browser_window_close

THE RISK

Critical Risk

Why browser_window_close needs a policy

Closing a browser window is an irreversible action — once closed, any unsaved state, session data, or form inputs in that window are lost and cannot be recovered. This matches the Destructive category (irreversibly destroys in-memory/session state). Severity is medium because the blast radius is limited to the current window's state rather than persistent data or finances.

From the tool's definition Close the current browser window (popup)

Documented attack patterns abuse exactly the kind of access browser_window_close gives an agent:

POLICY

How to control browser_window_close

PolicyLayer is an MCP gateway — it sits between your AI agents and Termux Browser Pilot, and nothing reaches the server without passing your rules. This is the rule we recommend for browser_window_close:

policy.json

{
  "version": "1",
  "default": "deny",
  "hide": [
    "browser_window_close"
  ]
}

browser_window_close disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.

Create a free account and register Termux Browser Pilot — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RESTRICT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Termux Browser Pilot tools

Destructive browser_auth_delete Delete a saved auth session. Destructive browser_console_clear Clear all captured console log messages. Destructive browser_cookies_clear Clear all browser cookies. Destructive browser_dialog_clear Clear all captured dialog messages. Destructive browser_events_clear Clear all captured DOM events. Destructive browser_headers_clear Clear all custom HTTP headers and remove fetch/XHR hooks. Destructive browser_mock_clear Remove response mock(s). Destructive browser_mutations_clear Clear all captured DOM mutations.

All 148 Termux Browser Pilot tools →

Destructive tools on other servers

Android Forensics ADB MCP Server create_full_backup 0xarchive web3_revoke_key Frida Game Hacking MCP clear_scan cPanel MCP Server clear_spam_box

Go deeper

Critical-risk tools in Termux Browser Pilot → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Blast radius → How much damage one compromised or confused agent can do — and how to bound it.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about browser_window_close

What does the browser_window_close tool do? +

Close the current browser window (popup). It is categorised as a Destructive tool in the Termux Browser Pilot MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.

How do I enforce a policy on browser_window_close? +

Register the Termux Browser Pilot MCP server in PolicyLayer and add a rule for browser_window_close: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Termux Browser Pilot. Nothing to install.

What risk level is browser_window_close? +

browser_window_close is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit browser_window_close? +

Yes. Add a rate_limit block to the browser_window_close rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block browser_window_close completely? +

Set action: deny in the PolicyLayer policy for browser_window_close. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides browser_window_close? +

browser_window_close is provided by the Termux Browser Pilot MCP server (salviz/termux-browser-pilot). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Termux Browser Pilot tool call.

Start from Termux Browser Pilot, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →