AI agents use browser_highlight to create or update resources in Wmux — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Wmux environment.
An AI agent can call browser_highlight faster than any human can review — one bad instruction and it creates or modifies resources in Wmux by the hundred, each call as confident as the last.
Attacks that exploit this kind of access
Visually highlight an element on the page by its ref number. Adds a red outline around the element. It is categorised as a Write tool in the Wmux MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Wmux MCP server in PolicyLayer and add a rule for browser_highlight: 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_highlight 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_highlight 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_highlight. 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_highlight 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_highlight 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.
Teams ship this data inside their own products. See what a licence covers →