Yes, the plugin is definitely at fault here. (It’s not the first one to be fair, but most others have patched the issue in the meantime.)
The error stems from passing null as the first parameter to the add_submenu_page function. WordPress has always expected a string there, and always used the argument as a string, e.g. by passing it to the strpos function. This hadn’t been a problem until PHP 8.1, where passing null to such functions causes a deprecation warning.
The issue is easily fixable by just using an empty string instead of null.
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This reply was modified 3 months, 1 week ago by loilo.
