Bug: https://gitlab.com/gitlab-org/gitlab-ce/issues/48415

--- a/lib/banzai/filter/sanitization_filter.rb
+++ b/lib/banzai/filter/sanitization_filter.rb
@@ -8,7 +8,7 @@
       TABLE_ALIGNMENT_PATTERN = /text-align: (?<alignment>center|left|right)/
 
       def whitelist
-        whitelist = super
+	whitelist = super.dup
 
         customize_whitelist(whitelist)