session_list

THE RISK

Low Risk

Why session_list needs a policy

This tool retrieves and displays information about existing browser sessions. It performs a read-only query of session state without modifying, executing, or destroying anything. The blast radius is minimal—an attacker could learn which tabs/sessions are open and their URLs, but cannot execute code, modify data, or access sensitive content beyond visible session metadata.

From the tool's definition Tool description states 'List all active browser sessions with their URLs and status' — a pure retrieval operation with no side effects. No modification, execution, or deletion occurs.

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

POLICY

How to control session_list

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "session_list": {}
  }
}

session_list is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Firefox MCP Server tools

Destructive debug_buffers_clear Clear accumulated debug data buffers to free memory and start fresh monitoring. Destructive browser_close Close the entire browser instance and clean up all sessions and resources. Destructive session_close Close a specific browser session and clean up its resources. Execute browser_launch Launch Firefox browser with multi-session support and comprehensive debugging capabilities Execute debug_monitoring_start Start or restart comprehensive monitoring for console logs, errors, network activity, and Execute element_wait Wait for specific elements to appear or become visible. Essential for handling dynamic con Execute javascript_execute Execute custom JavaScript code in the browser context. Powerful for advanced DOM manipulat Execute page_navigate Navigate to a specific URL in the browser. Works with any web page or web application.

All 29 Firefox MCP Server tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about session_list

What does the session_list tool do? +

List all active browser sessions with their URLs and status. Useful for managing multiple test scenarios. It is categorised as a Read tool in the Firefox MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on session_list? +

Register the Firefox MCP Server MCP server in PolicyLayer and add a rule for session_list: 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 Firefox MCP Server. Nothing to install.

What risk level is session_list? +

session_list is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit session_list? +

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

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

session_list is provided by the Firefox MCP Server MCP server (jediluke/firefox-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Firefox MCP Server tool call.

Start from Firefox MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →