MalDatabase
Provide malware datasets and threat intelligence feeds
Malware Archive / file sourcing.
MalShare API is a free Anti-Malware API that requires apiKey authentication, is served over HTTPS and does not support CORS, so it should be called from a server.
The MalShare Project is a community driven public malware repository that works to provide free access to malware samples and tooling to the infomation security community.
Details from malshare.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
The MalShare API is provided by MalShare (malshare.com). The MalShare Project is a community driven public malware repository that works to provide free access to malware samples and tooling to the infomation security community.
Yes. The MalShare 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 MalShare API uses apiKey authentication, so you need to register for credentials before making requests.
Not directly. The MalShare API does not allow CORS, so call it from a server, serverless function or proxy instead of front-end JavaScript.
Yes. The MalShare API is served over HTTPS, so it's safe to use in production.