Dear Olly,
Yesterday there was an update of the PHP version from 7.4.18 to 7.4.21 and a bug has been corrected in this version:
Fixed bug # 76359 (open_basedir bypass through adding “..”).
Source: https://www.php.net/ChangeLog-7.php#7.4.21
Unfortunately, certain WordPress plugins have not been developed correctly or have used the wrong syntax in the programming, so a warning is displayed.
Can you please correct the plugin name wppizza / wppizza-add-ingredients / wppizza-preorder / also for php 7.4.21 and publish an update.
You can also view the bug here. Deni-co.ch
Thank you very much.
Umut