CVE-2021-30492: Lack of Input Validation in zendesk_api_client_php for Zendesk Subdomain

Severity: Critical

CVSS Score: 10

### Impact Lack of input validation of the Zendesk subdomain could expose users of the library to Server Side Request Forgery (SSRF). ### Resolution Validate the provided Zendesk subdomain to be a valid subdomain in: * getAuthUrl * getAccessToken