Don't use URI.regexp to validate since it doens't have start/end anchors.

app/models/application_setting.rb

@@ -24,7 +24,7 @@ class ApplicationSetting < ActiveRecord::Base
 
   validates :home_page_url,
     allow_blank: true,
-    format: { with: URI::regexp(%w(http https)), message: "should be a valid url" },
+    format: { with: /\A#{URI.regexp(%w(http https))}\z/, message: "should be a valid url" },
     if: :home_page_url_column_exist
 
   validates_each :restricted_visibility_levels do |record, attr, value|

app/models/hooks/web_hook.rb

@@ -28,7 +28,7 @@ class WebHook < ActiveRecord::Base
   default_timeout Gitlab.config.gitlab.webhook_timeout
 
   validates :url, presence: true,
-                  format: { with: URI::regexp(%w(http https)), message: "should be a valid url" }
+                  format: { with: /\A#{URI.regexp(%w(http https))}\z/, message: "should be a valid url" }
 
   def execute(data)
     parsed_url = URI.parse(url)

app/models/project_services/bamboo_service.rb

@@ -25,7 +25,7 @@ class BambooService < CiService
 
   validates :bamboo_url,
     presence: true,
-    format: { with: URI::regexp },
+    format: { with: /\A#{URI.regexp}\z/ },
     if: :activated?
   validates :build_key, presence: true, if: :activated?
   validates :username,

app/models/project_services/external_wiki_service.rb

@@ -18,7 +18,7 @@ class ExternalWikiService < Service
   prop_accessor :external_wiki_url
   validates :external_wiki_url,
             presence: true,
-            format: { with: URI::regexp },
+            format: { with: /\A#{URI.regexp}\z/ },
             if: :activated?
 
   def title

app/models/project_services/teamcity_service.rb

@@ -25,7 +25,7 @@ class TeamcityService < CiService
 
   validates :teamcity_url,
     presence: true,
-    format: { with: URI::regexp }, if: :activated?
+    format: { with: /\A#{URI.regexp}\z/ }, if: :activated?
   validates :build_type, presence: true, if: :activated?
   validates :username,
     presence: true,