Undefined array key “HTTP_REFERER”

Can confirm, same here.

Guys…

Waiting for the fix of mistake from the developers I solved in this way:

I downloaded the file main.php from the path:
/wp-content/plugins/modern-events-calendar-lite/app/libraries/main.php

at line 6950 I had:
if(str_contains($_SERVER[‘HTTP_REFERER’],’external=1′)){

I changed into:
if(isset($_SERVER[‘HTTP_REFERER’]) && str_contains($_SERVER[‘HTTP_REFERER’], ‘external=1’)){

isset($_SERVER['HTTP_REFERER']) checks if the key exists before passing it to str_contains(), avoiding the warning.

Bye!
A.