Manual:$wgBlockOpenProxies

HTTP proxy (CDN) settings: $wgBlockOpenProxies
Automatic open proxy test on edit.
Introduced in version:1.2.4
Removed in version:1.22.0 (Gerrit change 87302; git #d7b953c2)
Allowed values:(boolean)
Default value:false

Details

edit

Automatic open proxy test on edit.

If you enable this, every editor's IP address will be scanned for open HTTP proxies.

You are strongly advised not to enable this. Many system administrators will report "hostile TCP port scans" to your ISP and ask for your server to be shut down... you have been warned!