respective .ini settings

bin/OpenSim.ini.example

@@ -1159,6 +1159,11 @@
   ;; If un-set / "" the module is disabled
   ;; ProfileServiceURL = ${Const|BaseURL}:${Const|PublicPort}
   
+  ;# {AllowUserProfileWebURLs} {} {allow user profiles web urls} {true false} true
+  ;; set this to false to prevent your users to be sent to unkown
+  ;; web sites by other users on their profiles
+  ; AllowUserProfileWebURLs = true
+
 [XBakes]
   ;# {URL} {} {Set URL for Baked texture service} {}
   ;; Sets the URL for the baked texture ROBUST service.

bin/OpenSimDefaults.ini

@@ -542,6 +542,10 @@
   ;; 
   ; ProfileURL = http://127.0.0.1:9000
   
+  ;; set this to false to prevent your users to be sent to unkown
+  ;; web sites by other users on their profiles
+  ; AllowUserProfileWebURLs = true
+
 
 [SMTP]
     enabled = false