Manual:$wgEnableSorbs

HTTP proxy (CDN) settings: $wgEnableSorbs
Use http.dnsbl.sorbs.net to check for open proxies.
Introduced in version:1.4.1
Deprecated in version:1.16.0
Removed in version:1.24.0 (Gerrit change 145738; git #1163efde)
Allowed values:(boolean)
Default value:false (1.4.11-1.23)
true (1.4.1-1.4.10)

Details

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Use http.dnsbl.sorbs.net to check for open proxies.