handle dangerous extensions

app/controllers/api/active_storage_blobs_proxy_controller.rb

@@ -11,6 +11,7 @@ module Api
     before_action :set_noindex_headers
     before_action :set_security_headers
 
+    # rubocop:disable Metrics
     def show
       blob_uuid, purp, exp = ApplicationRecord.signed_id_verifier.verified(params[:signed_uuid])
 
@@ -22,6 +23,12 @@ module Api
 
       blob = ActiveStorage::Blob.find_by!(uuid: blob_uuid)
 
+      if Submitters::DANGEROUS_EXTENSIONS.include?(blob.filename.extension.to_s.downcase)
+        Rollbar.error('Dangerous extension') if defined?(Rollbar)
+
+        return head :unprocessable_content
+      end
+
       attachment = blob.attachments.take
 
       @record = attachment.record
@@ -46,6 +53,7 @@ module Api
         end
       end
     end
+    # rubocop:enable Metrics
 
     private