diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1d5d614a5..e69f643ee 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Unreleased
 
+## 5.0.0
+
 ### Enhancements
 * Set multiple attribute for grouped selects also. [@ollym](https://github.com/ollym)
 * Removes or renames label classes. [Abduvakilov](https://github.com/Abduvakilov)
@@ -7,6 +9,18 @@
 * Update bootstrap generator template to match v4.3.x. [@m5o](https://github.com/m5o)
 * Allow "required" attribute in generated select elements of PriorityInput. [@mcountis](https://github.com/mcountis)
 
+### Bug fix
+* Do not call `#send` in form object to check whether the attribute is a file input. [@tegon](https://github.com/tegon)
+
+## Deprecations
+* The config `SimpleForm.file_methods` is deprecated and it has no effect. Simple Form now supports automatically discover of file inputs for the following Gems: activestorage, carrierwave, paperclip, refile and shrine. If you are using a custom method that is not from one of the supported Gems, please change your forms to pass the input type explicitly:
+
+```erb
+ <%= form.input :avatar, as: :file %>
+ ```
+
+See http://blog.plataformatec.com.br/2019/09/incorrect-access-control-in-simple-form-cve-2019-16676 for more information.
+
 ## 4.1.0
 
 ### Enhancements
diff --git a/Gemfile.lock b/Gemfile.lock
index 9f3964863..50bd0680f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    simple_form (4.1.0)
+    simple_form (5.0.0)
       actionpack (>= 5.0)
       activemodel (>= 5.0)
 
@@ -299,4 +299,4 @@ DEPENDENCIES
   simple_form!
 
 BUNDLED WITH
-   1.17.1
+   1.17.3
diff --git a/lib/generators/simple_form/templates/config/initializers/simple_form.rb b/lib/generators/simple_form/templates/config/initializers/simple_form.rb
index bb43c3364..0dc88e8c1 100644
--- a/lib/generators/simple_form/templates/config/initializers/simple_form.rb
+++ b/lib/generators/simple_form/templates/config/initializers/simple_form.rb
@@ -129,9 +129,6 @@
   # change this configuration to true.
   config.browser_validations = false
 
-  # Collection of methods to detect if a file type was given.
-  # config.file_methods = [ :mounted_as, :file?, :public_filename, :attached? ]
-
   # Custom mappings for input types. This should be a hash containing a regexp
   # to match as key, and the input type that will be used when the field name
   # matches the regexp as value.
diff --git a/lib/simple_form.rb b/lib/simple_form.rb
index 452e87b3b..2f603e8a0 100644
--- a/lib/simple_form.rb
+++ b/lib/simple_form.rb
@@ -38,6 +38,17 @@ def %{name}(wrapper_options)
 See https://github.com/plataformatec/simple_form/pull/997 for more information.
   WARN
 
+  FILE_METHODS_DEPRECATION_WARN = <<-WARN
+[SIMPLE_FORM] SimpleForm.file_methods is deprecated and has no effect.
+
+Since version 5, Simple Form now supports automatically discover of file inputs for the following Gems: activestorage, carrierwave, paperclip, refile and shrine.
+If you are using a custom method that is not from one of the supported Gems, please change your forms to pass the input type explicitly:
+
+    <%= form.input :avatar, as: :file %>
+
+See http://blog.plataformatec.com.br/2019/09/incorrect-access-control-in-simple-form-cve-2019-16676 for more information.
+  WARN
+
   @@configured = false
 
   def self.configured? #:nodoc:
@@ -120,10 +131,6 @@ def self.configured? #:nodoc:
   mattr_accessor :browser_validations
   @@browser_validations = true
 
-  # Collection of methods to detect if a file type was given.
-  mattr_accessor :file_methods
-  @@file_methods = %i[mounted_as file? public_filename attached?]
-
   # Custom mappings for input types. This should be a hash containing a regexp
   # to match as key, and the input type that will be used when the field name
   # matches the regexp as value, such as { /count/ => :integer }.
@@ -265,6 +272,16 @@ def self.form_class=(value)
     @@form_class = value
   end
 
+  def self.file_methods=(file_methods)
+    ActiveSupport::Deprecation.warn(FILE_METHODS_DEPRECATION_WARN, caller)
+    @@file_methods = file_methods
+  end
+
+  def self.file_methods
+    ActiveSupport::Deprecation.warn(FILE_METHODS_DEPRECATION_WARN, caller)
+    @@file_methods
+  end
+
   # Default way to setup Simple Form. Run rails generate simple_form:install
   # to create a fresh initializer with all configuration values.
   def self.setup
diff --git a/lib/simple_form/form_builder.rb b/lib/simple_form/form_builder.rb
index 5f1f2e5ad..4e8a73cc3 100644
--- a/lib/simple_form/form_builder.rb
+++ b/lib/simple_form/form_builder.rb
@@ -572,9 +572,28 @@ def find_custom_type(attribute_name)
       }.try(:last) if SimpleForm.input_mappings
     end
 
+    # Internal: Try to discover whether an attribute corresponds to a file or not.
+    #
+    # Most upload Gems add some kind of attributes to the ActiveRecord's model they are included in.
+    # This method tries to guess if an attribute belongs to some of these Gems by checking the presence
+    # of their methods using `#respond_to?`.
+    #
+    # Note: This does not support multiple file upload inputs, as this is very application-specific.
+    #
+    # The order here was choosen based on the popularity of Gems and for commodity - e.g. the method
+    # with the suffix `_url` is present in three Gems, so it's checked with priority:
+    #
+    # - `#{attribute_name}_attachment` - ActiveStorage >= `5.2` and Refile >= `0.2.0` <= `0.4.0`
+    # - `#{attribute_name}_url` - Shrine >= `0.9.0`, Refile >= `0.6.0` and CarrierWave >= `0.2.1`
+    # - `#{attribute_name}_attacher` - Refile >= `0.4.0` and Shrine >= `0.9.0`
+    # - `#{attribute_name}_file_name` - Paperclip ~> `2.0` (added for backwards compatibility)
+    #
+    # Returns a Boolean.
     def file_method?(attribute_name)
-      file = @object.send(attribute_name) if @object.respond_to?(attribute_name)
-      file && SimpleForm.file_methods.any? { |m| file.respond_to?(m) }
+      @object.respond_to?("#{attribute_name}_attachment") ||
+        @object.respond_to?("#{attribute_name}_url") ||
+        @object.respond_to?("#{attribute_name}_attacher") ||
+        @object.respond_to?("#{attribute_name}_file_name")
     end
 
     def find_attribute_column(attribute_name)
diff --git a/lib/simple_form/version.rb b/lib/simple_form/version.rb
index 7cba90867..53f698631 100644
--- a/lib/simple_form/version.rb
+++ b/lib/simple_form/version.rb
@@ -1,4 +1,4 @@
 # frozen_string_literal: true
 module SimpleForm
-  VERSION = "4.1.0".freeze
+  VERSION = "5.0.0".freeze
 end
diff --git a/test/form_builder/general_test.rb b/test/form_builder/general_test.rb
index f8732514e..196a46fb9 100644
--- a/test/form_builder/general_test.rb
+++ b/test/form_builder/general_test.rb
@@ -239,31 +239,24 @@ def with_custom_form_for(object, *args, &block)
     assert_select 'form select#user_updated_at_1i.datetime'
   end
 
-  test 'builder generates file for file columns' do
-    @user.avatar = MiniTest::Mock.new
-    @user.avatar.expect(:public_filename, true)
-    @user.avatar.expect(:!, false)
-
-    with_form_for @user, :avatar
-    assert_select 'form input#user_avatar.file'
+  test 'builder generates file input for ActiveStorage >= 5.2 and Refile >= 0.2.0 <= 0.4.0' do
+    with_form_for UserWithAttachment.build, :avatar
+    assert_select 'form input#user_with_attachment_avatar.file'
   end
 
-  test 'builder generates file for activestorage entries' do
-    @user.avatar = MiniTest::Mock.new
-    @user.avatar.expect(:attached?, false)
-    @user.avatar.expect(:!, false)
-
-    with_form_for @user, :avatar
-    assert_select 'form input#user_avatar.file'
+  test 'builder generates file input for Shrine >= 0.9.0, Refile >= 0.6.0 and CarrierWave >= 0.2.1' do
+    with_form_for UserWithAttachment.build, :cover
+    assert_select 'form input#user_with_attachment_cover.file'
   end
 
-  test 'builder generates file for attributes that are real db columns but have file methods' do
-    @user.home_picture = MiniTest::Mock.new
-    @user.home_picture.expect(:mounted_as, true)
-    @user.home_picture.expect(:!, false)
+  test 'builder generates file input for Refile >= 0.4.0 and Shrine >= 0.9.0' do
+    with_form_for UserWithAttachment.build, :profile_image
+    assert_select 'form input#user_with_attachment_profile_image.file'
+  end
 
-    with_form_for @user, :home_picture
-    assert_select 'form input#user_home_picture.file'
+  test 'builder generates file input for Paperclip ~> 2.0' do
+    with_form_for UserWithAttachment.build, :portrait
+    assert_select 'form input#user_with_attachment_portrait.file'
   end
 
   test 'build generates select if a collection is given' do
diff --git a/test/support/models.rb b/test/support/models.rb
index 9801a7a2c..82530de7e 100644
--- a/test/support/models.rb
+++ b/test/support/models.rb
@@ -333,3 +333,21 @@ def name
 
 class UserNumber1And2 < User
 end
+
+class UserWithAttachment < User
+  def avatar_attachment
+    OpenStruct.new
+  end
+
+  def cover_url
+    "/uploads/cover.png"
+  end
+
+  def profile_image_attacher
+    OpenStruct.new
+  end
+
+  def portrait_file_name
+    "portrait.png"
+  end
+end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 0dccc0212..8797e93a5 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -91,4 +91,5 @@ def company_user_path(*args)
   alias :validating_user_path :user_path
   alias :validating_users_path :user_path
   alias :other_validating_user_path :user_path
+  alias :user_with_attachment_path :user_path
 end