WPVulnDB API Pricing Inquiry
On October 1st, 2019, WPVulnDB API version 2 (free API) will no longer be usable. If you want to use the Vulnerability Checker Extension, you will need to move to API version 3 (Paid API) and register a free account on wpvulndb.com. Once registered, you will be given an API Token to insert into the Vulnerability Checker Extension.
The price for unlimited API usage depends on the number of WordPress sites that you intend to scan.