MISP Modules: external tools endpoint leaks stored API keys without login

The MISP Modules website component contains an information disclosure vulnerability in the external tools management interface. The /external_tools/list endpoint returned stored API keys (the api_key field) in its JSON response via the ExternalTools model serializer. Additionally, the browser-based edit form pre-populated the API key input field with the stored credential value, exposing it in the DOM.

The /external_tools/list endpoint is accessible without authentication (the regression tests verify the response for both authenticated and unauthenticated clients), meaning any network-reachable client could retrieve the API keys for all configured external tools. These keys are used by the server to authenticate submissions to external analysis or enrichment services, so their disclosure allows an attacker to impersonate the MISP instance or directly access those external services.

The vulnerability also affected the edit workflow: the change_config endpoint previously required the API key to be present and non-empty on every save, forcing the key to round-trip through the client. The browser JavaScript stored the key in a reactive state object and updated the in-memory tool list with the credential value, further increasing the window of exposure in client-side memory and network traffic.

Affected component: the website sub-application of MISP Modules, specifically the external_tools module (serializer in models.py, list endpoint, and the external_tools_index.html template). The impact is limited to confidentiality of the stored API keys; no integrity or availability impact on the MISP Modules website itself is indicated by the patch.