set_cookies · Chromium ARM64 Browser MCP: Risk & Policy

WHAT IT DOES

What set_cookies does on Chromium ARM64 Browser

AI agents use set_cookies to create or update resources in Chromium ARM64 Browser — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Chromium ARM64 Browser environment.

WHY IT NEEDS A POLICY

Why set_cookies needs a policy

This tool creates or modifies authentication state in the browser by importing cookies. While cookies are not data in the traditional sense, setting them changes the browser's authenticated session state, which is a reversible modification. The high severity reflects that misuse could allow an AI agent to impersonate authenticated users across SaaS platforms or gain unauthorized access to accounts.

From the tool's definition Tool description states 'Import cookies...so the browser is authenticated' and explicitly mentions 'Auth-critical cookies like x.com auth_token'. The name 'set_cookies' indicates modification of browser cookie state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_cookies Rate-limited

set_cookies stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_cookies": {
      "limits": [
        {
          "counter": "set_cookies_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Chromium ARM64 Browser, so you can run agents against it safely.

FAQ

Questions about set_cookies

What does the set_cookies tool do? +

Import cookies (e.g. exported after logging in elsewhere) so the browser is authenticated without scripting the login form. Auth-critical cookies like x.com auth_token are httpOnly and must come from a real export (DevTools / Cookie-Editor), not document.cookie. It is categorised as a Write tool in the Chromium ARM64 Browser MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_cookies? +

Register the Chromium ARM64 Browser MCP server in PolicyLayer and add a rule for set_cookies: 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 Chromium ARM64 Browser. Nothing to install.

What risk level is set_cookies? +

set_cookies is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_cookies? +

Yes. Add a rate_limit block to the set_cookies 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 set_cookies completely? +

Set action: deny in the PolicyLayer policy for set_cookies. 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 set_cookies? +

set_cookies is provided by the Chromium ARM64 Browser MCP server (nfodor/mcp-chromium-arm64). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.