// MCP TOOL REFERENCE

generate_xss_callback

Generate XSS (Cross-Site Scripting) callback payloads for bug bounty testing. Creates JavaScript payloads that ping your webhook when executed, useful for detecting blind XSS.

ServerWebhook Site MCP Server
CategoryExecute

How to control generate_xss_callback ↓

WHAT IT DOES

What generate_xss_callback does on Webhook Site MCP Server

AI agents invoke generate_xss_callback to trigger actions in Webhook Site MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

THE RISK

High Risk

Why generate_xss_callback needs a policy

This tool generates executable JavaScript attack payloads designed to be injected into web pages. While framed as bug bounty testing, it produces XSS exploit code intended to execute in victims' browsers. This is an Execute-category tool as it creates code that triggers external operations (webhook callbacks) when run in target environments.

From the tool's definition Generate XSS (Cross-Site Scripting) callback payloads... Creates JavaScript payloads that ping your webhook when executed, useful for detecting blind XSS

Documented attack patterns abuse exactly the kind of access generate_xss_callback gives an agent:

POLICY

How to control generate_xss_callback

PolicyLayer is an MCP gateway — it sits between your AI agents and Webhook Site MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for generate_xss_callback:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "generate_xss_callback": {
      "limits": [
        {
          "counter": "generate_xss_callback_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

generate_xss_callback stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register Webhook Site MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Webhook Site MCP Server tools

Destructive delete_all_requests Delete all requests from a webhook, optionally filtered by date range or query. Destructive delete_request Delete a specific request from a webhook. Destructive delete_webhook Delete a webhook.site endpoint and all its data. Execute generate_ssrf_payload Generate SSRF (Server-Side Request Forgery) test payloads for bug bounty testing. Creates Execute send_multiple_requests Send multiple requests to a webhook in batch. Useful for load testing or sending multiple Execute send_to_webhook Send a POST request with JSON data to a webhook.site endpoint. Write create_webhook Create a new webhook.site endpoint. Returns the unique token/URL for the webhook. Write create_webhook_with_config Create a new webhook.site endpoint with custom configuration (response content, status, ti

All 23 Webhook Site MCP Server tools →

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Go deeper

High-risk tools in Webhook Site MCP Server → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about generate_xss_callback

What does the generate_xss_callback tool do? +

Generate XSS (Cross-Site Scripting) callback payloads for bug bounty testing. Creates JavaScript payloads that ping your webhook when executed, useful for detecting blind XSS. It is categorised as a Execute tool in the Webhook Site MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on generate_xss_callback? +

Register the Webhook Site MCP Server MCP server in PolicyLayer and add a rule for generate_xss_callback: 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 Webhook Site MCP Server. Nothing to install.

What risk level is generate_xss_callback? +

generate_xss_callback is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit generate_xss_callback? +

Yes. Add a rate_limit block to the generate_xss_callback 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.

How do I block generate_xss_callback completely? +

Set action: deny in the PolicyLayer policy for generate_xss_callback. 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.

What MCP server provides generate_xss_callback? +

generate_xss_callback is provided by the Webhook Site MCP Server MCP server (zebbern/webhook-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Webhook Site MCP Server tool call.

Start from Webhook Site MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →

Free to start. No card required.

23 Webhook Site MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.