Register or update the HTTPS webhook URL that Viber calls for incoming events (messages, subscriptions, delivery receipts). Call once during bot setup or when the URL changes. Replaces any existing webhook. Returns the confirmed list of subscribed event types.
AI agents use set_webhook to create or update resources in Viber — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Viber environment.
This tool creates or modifies configuration data (webhook URL registration) rather than destroying it. The severity is high because misconfiguration could redirect all incoming bot events to an attacker-controlled server, leading to message interception, credential theft, or bot hijacking.
From the tool's definition Tool description states it will 'Register or update the HTTPS webhook URL' and 'Replaces any existing webhook'. The action is reversible (can be updated again) but modifies bot infrastructure configuration.
Attacks that exploit this kind of access
Register or update the HTTPS webhook URL that Viber calls for incoming events (messages, subscriptions, delivery receipts). Call once during bot setup or when the URL changes. Replaces any existing webhook. Returns the confirmed list of subscribed event types. It is categorised as a Write tool in the Viber MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Viber MCP server in PolicyLayer and add a rule for set_webhook: 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 Viber. Nothing to install.
set_webhook 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 set_webhook 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 set_webhook. 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.
set_webhook is provided by the Viber MCP server (serhiizghama/viber-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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