To promote better security, we plan to move to Smarty 4, which is not compatible with SmartyBC, in the near future. If you use certain Smarty tags in your customizations, you must remove them now.
We plan to permanently remove support for legacy Smarty tags in WHMCS 9.0. You must remove these tags from your customizations on self-hosted WHMCS installations.
Smarty Security Policies are security hardening measures that protect a system. WHMCS applies a Smarty Security Policy for system-wide use and a mail policy for stored and dynamic email-based templates.