diff --git a/Gemfile b/Gemfile
index 8b6a215c..d1334627 100644
--- a/Gemfile
+++ b/Gemfile
@@ -46,6 +46,7 @@ gem 'devise-i18n'
 gem 'devise_invitable'
 gem 'email_address'
 gem 'exception_notification'
+gem 'fast_blank'
 gem 'friendly_id'
 gem 'hamlit-rails'
 gem 'hiredis'
diff --git a/Gemfile.lock b/Gemfile.lock
index 2ce54845..536c439e 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -170,6 +170,7 @@ GEM
     factory_bot_rails (5.2.0)
       factory_bot (~> 5.2.0)
       railties (>= 4.2.0)
+    fast_blank (1.0.0)
     ffi (1.13.1)
     flamegraph (0.9.5)
     forwardable-extended (2.6.0)
@@ -525,6 +526,7 @@ DEPENDENCIES
   email_address
   exception_notification
   factory_bot_rails
+  fast_blank
   flamegraph
   friendly_id
   haml-lint
diff --git a/app/models/metadata_belongs_to.rb b/app/models/metadata_belongs_to.rb
index 89b4676f..941273a7 100644
--- a/app/models/metadata_belongs_to.rb
+++ b/app/models/metadata_belongs_to.rb
@@ -20,7 +20,7 @@ class MetadataBelongsTo < MetadataRelatedPosts
   def validate
     super
 
-    errors << I18n.t('metadata.belongs_to.missing_post') unless !value.blank? && posts.find(sanitize(value), uuid: true)
+    errors << I18n.t('metadata.belongs_to.missing_post') unless post_exists?
 
     errors.empty?
   end
@@ -30,4 +30,8 @@ class MetadataBelongsTo < MetadataRelatedPosts
   def sanitize(uuid)
     uuid.gsub(/[^a-f0-9\-]/, '')
   end
+
+  def post_exists?
+    !value.blank? && posts.find(sanitize(value), uuid: true)
+  end
 end
diff --git a/app/models/metadata_markdown_content.rb b/app/models/metadata_markdown_content.rb
index 890ffff5..509088db 100644
--- a/app/models/metadata_markdown_content.rb
+++ b/app/models/metadata_markdown_content.rb
@@ -9,8 +9,8 @@ class MetadataMarkdownContent < MetadataContent
   end
 
   # XXX: No sanitizamos acá porque se escapan varios símbolos de
-  # markdown y se eliminan autolinks.  Mejor es habilitar la generación
-  # SAFE de CommonMark en la configuración del sitio.
+  # markdown y se eliminan autolinks.  Mejor es deshabilitar la
+  # generación SAFE de CommonMark en la configuración del sitio.
   def sanitize(string)
     string
   end
diff --git a/app/models/metadata_string.rb b/app/models/metadata_string.rb
index 4cc2ff1f..d1008748 100644
--- a/app/models/metadata_string.rb
+++ b/app/models/metadata_string.rb
@@ -6,4 +6,16 @@ class MetadataString < MetadataTemplate
   def default_value
     ''
   end
+
+  private
+
+  # No se permite HTML en las strings
+  def sanitize(string)
+    return '' if string.blank?
+
+    sanitizer.sanitize(string.strip,
+                       tags: [],
+                       attributes: [],
+                       scrubber: scrubber).strip.html_safe
+  end
 end
diff --git a/app/models/metadata_template.rb b/app/models/metadata_template.rb
index fcca637f..6d490b5f 100644
--- a/app/models/metadata_template.rb
+++ b/app/models/metadata_template.rb
@@ -39,7 +39,7 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
   def validate
     self.errors = []
 
-    errors << I18n.t("metadata.cant_be_empty") unless can_be_empty?
+    errors << I18n.t('metadata.cant_be_empty') unless can_be_empty?
 
     errors.empty?
   end