The hookpoint is used to create the invoice for selling premium domains. Without the hookpoint working, all invoices for selling premium domains will result in normal selling prices for premium domains. If you have updated to whmcs 5.3.7 and using our domain registrar module (LCDRM), then we suggest to disable selling premium domains temporarily.
There is no update expected from WHMCS to resolve these critical issues. We therefore share our workaround for those user who consider IDN domain register and the Hook point "InvoiceCreationPreEmail" as critical:
Workaround for WHMCS v5.3.7
1. Obtain WHMCS v5.3.6. You can download it from the whmcs client area
2. Extract the zipfile and upload the following files: