prevent sql injection attacks by escaping quotes in column names

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -169,7 +169,7 @@ def quote(value, column = nil)
       end
 
       def quote_column_name(name) #:nodoc:
-        @quoted_column_names[name] ||= "`#{name}`"
+        @quoted_column_names[name] ||= "`#{name.to_s.gsub('`', '``')}`"
       end
 
       def quote_table_name(name) #:nodoc:

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -250,7 +250,7 @@ def type_cast(value, column)
       end
 
       def quote_column_name(name) #:nodoc:
-        @quoted_column_names[name] ||= "`#{name}`"
+        @quoted_column_names[name] ||= "`#{name.to_s.gsub('`', '``')}`"
       end
 
       def quote_table_name(name) #:nodoc:

activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb

@@ -148,7 +148,7 @@ def quote_string(s) #:nodoc:
       end
 
       def quote_column_name(name) #:nodoc:
-        %Q("#{name}")
+        %Q("#{name.to_s.gsub('"', '""')}")
       end
 
       # Quote date/time values for use in SQL input. Includes microseconds

activerecord/test/cases/base_test.rb

@@ -67,6 +67,23 @@ def setup
 class BasicsTest < ActiveRecord::TestCase
   fixtures :topics, :companies, :developers, :projects, :computers, :accounts, :minimalistics, 'warehouse-things', :authors, :categorizations, :categories, :posts
 
+  def test_column_names_are_escaped
+    conn      = ActiveRecord::Base.connection
+    classname = conn.class.name[/[^:]*$/]
+    badchar   = {
+      'SQLite3Adapter'    => '"',
+      'MysqlAdapter'      => '`',
+      'Mysql2Adapter'     => '`',
+      'PostgreSQLAdapter' => '"',
+      'OracleAdapter'     => '"',
+    }.fetch(classname) {
+      raise "need a bad char for #{classname}"
+    }
+
+    quoted = conn.quote_column_name "foo#{badchar}bar"
+    assert_equal("#{badchar}foo#{badchar * 2}bar#{badchar}", quoted)
+  end
+
   def test_columns_should_obey_set_primary_key
     pk = Subscriber.columns.find { |x| x.name == 'nick' }
     assert pk.primary, 'nick should be primary key'