Provide malware datasets and threat intelligence feeds.
MalDatabase API is a free Anti-Malware API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from maldatabase.com.

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Malware Archive / file sourcing
The MalDatabase API is provided by Maldatabase (maldatabase.com).
Yes. The MalDatabase API is listed in the Anti-Malware category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
Yes. The MalDatabase API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the MalDatabase API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The MalDatabase API is served over HTTPS, so it's safe to use in production.