type:
constant
name:
CHECK_REFERRER
purpose:
Verify that the referring web page is allowed
allowed:
true false 0 1
default:
1
category:
security

This is a small check on validity of a request and will not protect completely. But it won't hurt either.

In order to allow referrers you know, you can use allowed_referrers

If you continuously get “Access denied” when using phpList, you will want to switch this off.