Upload one or multiple files to file input
AI agents use browser_file_upload to create or update resources in Fast Playwright MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fast Playwright MCP environment.
This tool uploads files to a file input element in the browser, which is a write operation that sends data to a remote service. It has high severity because an AI agent could misuse it to upload sensitive files, malware, or large amounts of data to arbitrary web endpoints without user awareness.
From the tool's definition Upload one or multiple files to file input
Documented attack patterns abuse exactly the kind of access browser_file_upload gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fast Playwright MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for browser_file_upload:
{
"version": "1",
"default": "deny",
"tools": {
"browser_file_upload": {
"limits": [
{
"counter": "browser_file_upload_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}browser_file_upload 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.
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Upload one or multiple files to file input. It is categorised as a Write tool in the Fast Playwright MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fast Playwright MCP server in PolicyLayer and add a rule for browser_file_upload: 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 Fast Playwright MCP. Nothing to install.
browser_file_upload is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the browser_file_upload 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.
Set action: deny in the PolicyLayer policy for browser_file_upload. 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.
browser_file_upload is provided by the Fast Playwright MCP server (tontoko/fast-playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 34 Fast Playwright MCP tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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34 Fast Playwright MCP tools catalogued and risk-classified — across an index of 42,500+ MCP servers.