AI agents use add_url_to_filter to create or update resources in Fortimanager — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fortimanager environment.
This tool creates or modifies filter rules by adding URLs, which is a reversible write operation. It could have security implications if an attacker adds malicious URLs to allowed lists or blocks legitimate traffic, but it's not destructive (reversible), not financial, and not direct code execution. Severity is high because filter manipulation affects network security policy enforcement.
From the tool's definition Tool name is 'add_url_to_filter' which indicates creating or adding a URL entry to a filter list. The 'add' operation is inherently a write/create action.
Documented attack patterns abuse exactly the kind of access add_url_to_filter gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fortimanager, and nothing reaches the server without passing your rules. This is the rule we recommend for add_url_to_filter:
{
"version": "1",
"default": "deny",
"tools": {
"add_url_to_filter": {
"limits": [
{
"counter": "add_url_to_filter_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_url_to_filter stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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add_url_to_filter. It is categorised as a Write tool in the Fortimanager MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fortimanager MCP server in PolicyLayer and add a rule for add_url_to_filter: 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 Fortimanager. Nothing to install.
add_url_to_filter 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 add_url_to_filter 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 add_url_to_filter. 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.
add_url_to_filter is provided by the Fortimanager MCP server (jmpijll/fortimanager-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Fortimanager, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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