Try this, I can't test it as far as the mod_security rule goes so you can be the guinea pig.
It's just temp solution if it works but it will help identify the problem whether it works or not.
Open /includes/functions.php
Find:
Code: Select all
'S_LOGIN_REDIRECT' => $s_login_redirect,
Replace with (note: you need to edit in the root of your phpBB forum for https://www.example.com/forum/):
Code: Select all
'S_LOGIN_REDIRECT' => str_replace( './../' , 'https://www.example.com/forum/' , $s_login_redirect),
Before uplaoding to your server rename existing functions.php to functions.php.bak so you have easy fallback to replace original file. Make sure mod_security is enabled. This may not be required but purge phpBB's cache. You may need to logout of forum to trigger login for ACP.
“Results! Why, man, I have gotten a lot of results! I have found several thousand things that won’t work.”
Attributed - Thomas Edison