ThumbGate Verification evidence
guide | browser automation safety

# Browser automation safety needs explicit approval boundaries

Browser agents can click, type, and navigate for you, but they also widen prompt-injection and cross-app integration risk. ThumbGate adds approval boundaries, auditability, and a native messaging audit before those bridges turn into silent blast-radius expansion.

👍 Thumbs up reinforces good behavior
👎 Thumbs down blocks repeated mistakes

## Why this page exists

- Browser automation is useful because it has real permissions, which is exactly why it needs governance.
- Prompt injection becomes more dangerous when an extension can reach a local executable through a browser bridge.
- ThumbGate gives teams a first action now: audit native messaging hosts, then require explicit approval before browser-use connectors expand.

## Why browser-use changes the threat model

Browser agents do not just read text. They can click buttons, fill forms, switch tabs, and sometimes bridge into local binaries. That means the blast radius is no longer only "bad output" but "real actions on live websites and local systems."

Once browser automation enters the stack, prompt injection stops being an abstract model weakness and becomes a workflow-governance problem. The right control is not more prompt advice. It is a hard boundary around what the agent is allowed to connect, install, and execute.

## What to audit first

- Which browser extensions hold automation permissions such as debugger, tabs, downloads, and nativeMessaging.
- Whether the desktop app or CLI has registered native messaging hosts for browsers you did not explicitly connect.
- Whether host manifests point to live local binaries and whether those binaries sit outside the browser sandbox.
- Whether browser-use runs default to ask-before-acting or silently expand capability before a human approves them.

## How ThumbGate fits

ThumbGate is the approval and enforcement layer around browser-use. Start by running npx thumbgate native-messaging-audit. Then gate future connector installs, record who approved them, and turn browser-bridge mistakes into Pre-Action Checks before the same pattern repeats.

## FAQ

Why is browser automation riskier than ordinary chat?

Because the agent can take real actions in a browser and may also reach local executables through native messaging bridges. That turns prompt injection and permission drift into operational risk, not just output-quality risk.

What should a team do before enabling browser-use broadly?

Audit native messaging hosts, review extension permissions, keep ask-before-acting enabled by default, and require explicit approval for any cross-app connector that expands the agent runtime beyond the browser sandbox.