Take a screenshot of the current page or a specific element. Returns the image as base64-encoded PNG. Requires browser_open to be called first to establish a connection, even if a browser panel is already visible.
AI agents call browser_screenshot to retrieve information from Wmux without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
browser_screenshot retrieves visual information from a browser session. It reads and returns data (screenshot as base64 PNG) without creating, modifying, deleting, or executing operations. This is a pure Read operation. Severity is low because screenshots pose minimal risk—they expose only what is already visible on screen to the session holder, with no capability to alter state or trigger external operations.
From the tool's definition Tool description: 'Take a screenshot of the current page or a specific element. Returns the image as base64-encoded PNG.' This is a retrieval operation that captures visual state without modifying, deleting, or executing code.
Attacks that exploit this kind of access
Take a screenshot of the current page or a specific element. Returns the image as base64-encoded PNG. Requires browser_open to be called first to establish a connection, even if a browser panel is already visible. It is categorised as a Read tool in the Wmux MCP Server, which means it retrieves data without modifying state.
Register the Wmux MCP server in PolicyLayer and add a rule for browser_screenshot: 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 Wmux. Nothing to install.
browser_screenshot is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the browser_screenshot 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_screenshot. 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_screenshot is provided by the Wmux MCP server (openwong2kim/wmux). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
browser_screenshot is one line of Wmux's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
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