Following the publication of a security advisory today [ https://blog.whmcs.com/?t=76310 ] we have identified two deficiencies in our build automation for the 5.2.6 build 3 package.

v5.2.6 build 4 addresses the below issues:
Ship decoded ./crons/config.php
Remove langupdate.php throughout.

The updated build contains no code or functionality changes.

Note: If you have either /lang/langupdate.php or /admin/lang/adminlangupdate.php present in your installation we recommend removing them.