diff --git a/app/models/metadata_content.rb b/app/models/metadata_content.rb
index a14e19f7..4105ffcc 100644
--- a/app/models/metadata_content.rb
+++ b/app/models/metadata_content.rb
@@ -14,4 +14,44 @@ class MetadataContent < MetadataTemplate
   def front_matter?
     false
   end
+
+  private
+
+  # Limpiar el HTML que recibimos
+  #
+  # TODO: En lugar de comprobar el Content Type acá, restringir los
+  # tipos de archivo a aceptar en ActiveStorage.
+  def sanitize(html_string)
+    html = Nokogiri::HTML.fragment(super html_string)
+    elements = 'img,audio,video,iframe'
+
+    # Eliminar elementos sin src y comprobar su origen
+    html.css(elements).each do |element|
+      unless element['src']
+        element.remove
+        next
+      end
+
+      begin
+        uri = URI element['src']
+
+        # No permitimos recursos externos
+        element.remove unless uri.hostname.end_with? Site.domain
+      rescue URI::Error
+        element.remove
+      end
+    end
+
+    # Eliminar figure sin contenido
+    html.css('figure').each do |figure|
+      figure.remove if figure.css(elements).empty?
+    end
+
+    # Los videos y audios necesitan controles
+    html.css('audio,video').each do |resource|
+      resource['controls'] = true
+    end
+
+    html.to_s.html_safe
+  end
 end