Browserbase MCP

All 9 findings

1. critical
   Tool `browserbase_stagehand_agent` exposes a code/command execution surface· browserbase_stagehand_agentexcessive agency

   `browserbase_stagehand_agent` looks like it executes code or shell commands (Execute a task autonomously using Gemini Computer Use agent. The agent will navigate and interact with web pages to complete the given task.). Arbitrary execution is the maximal authority a tool can hold -- it subsumes every other caveat, so it should never be exposed to an agent without a hard sandbox and an explicit, narrowly-scoped capability.

   fix: Do not expose raw code/shell execution to an agent. If unavoidable, run it in a disposable sandbox with no network + no host FS, gate it behind a capframe-bind capability scoped to an allow-list of commands, and require holder-of-key proof per call.

2. high
   Tool `browserbase_session_create` name implies a side effect that is not declared· browserbase_session_createexcessive agency

   `browserbase_session_create` looks like a side-effecting tool (its name contains a mutation verb), but its `side_effects` declaration is []. A policy synthesizer cannot produce safe rules for this tool because it cannot tell what it actually does.

   fix: Declare the tool's true side effects explicitly. If the tool is genuinely read-only, rename it to match (e.g. `email.preview` rather than `email.send`).

3. medium
   Tool `browserbase_session_create` accepts unconstrained string input· browserbase_session_createunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `sessionId`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.

4. medium
   Tool `browserbase_stagehand_navigate` accepts unconstrained string input· browserbase_stagehand_navigateunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `url`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.

5. medium
   Tool `browserbase_stagehand_act` accepts unconstrained string input· browserbase_stagehand_actunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `action`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.

6. medium
   Tool `browserbase_stagehand_extract` accepts unconstrained string input· browserbase_stagehand_extractunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `instruction`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.

7. medium
   Tool `browserbase_stagehand_observe` accepts unconstrained string input· browserbase_stagehand_observeunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `instruction`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.

8. medium
   Tool `browserbase_screenshot` accepts unconstrained string input· browserbase_screenshotunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `name`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.

9. medium
   Tool `browserbase_stagehand_agent` accepts unconstrained string input· browserbase_stagehand_agentunconstrained input

   The following string parameter(s) have no `maxLength` constraint: `prompt`. Unbounded strings let an attacker stuff arbitrary payloads through the tool, including indirect-injection content.

   fix: Add a `maxLength` to each string property, or constrain with an `enum` or `pattern`. Most legitimate tool inputs fit under a few hundred bytes.