execute_script · MCP Selenium WebDriver MCP: Risk & Policy

WHAT IT DOES

What execute_script does on MCP Selenium WebDriver

AI agents invoke execute_script to trigger actions in MCP Selenium WebDriver. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why execute_script needs a policy

Executing arbitrary JavaScript in a browser can perform any action available to JavaScript in that context: modify DOM, steal cookies/session tokens, exfiltrate data, redirect users, trigger unintended actions, or interact with web applications in unauthorized ways. The high blast radius and dependency on user-supplied arguments (the script to execute) classify this as Execute severity.

From the tool's definition Tool name 'execute_script' combined with description 'Ejecuta JavaScript en el navegador' (Executes JavaScript in the browser) explicitly indicates code execution capability. This allows running arbitrary JavaScript within the browser context.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

execute_script Rate-limited

execute_script stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "execute_script": {
      "limits": [
        {
          "counter": "execute_script_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about execute_script

What does the execute_script tool do? +

Ejecuta JavaScript en el navegador. It is categorised as a Execute tool in the MCP Selenium WebDriver MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on execute_script? +

Register the MCP Selenium WebDriver MCP server in PolicyLayer and add a rule for execute_script: 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 MCP Selenium WebDriver. Nothing to install.

What risk level is execute_script? +

execute_script is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit execute_script? +

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

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

execute_script is provided by the MCP Selenium WebDriver MCP server (nixon-suarez/mcp-selenium-webdriver). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.