IP/domain/URL reputation.
AbuseIPDB API is a free Anti-Malware API that requires apiKey authentication, is served over HTTPS and has unconfirmed CORS support.
Details from docs.abuseipdb.com.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Provide malware datasets and threat intelligence feeds
Malware Archive / file sourcing
The AbuseIPDB API is provided by AbuseIPDB APIv2 Documentation (docs.abuseipdb.com).
Yes. The AbuseIPDB 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 AbuseIPDB API uses apiKey authentication, so you need to register for credentials before making requests.
CORS support for the AbuseIPDB API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The AbuseIPDB API is served over HTTPS, so it's safe to use in production.