=== modified file 'Mailman/Cgi/edithtml.py'
--- Mailman/Cgi/edithtml.py	2018-06-17 23:47:34 +0000
+++ Mailman/Cgi/edithtml.py	2018-06-30 07:15:35 +0000
@@ -210,7 +210,11 @@
         doc.AddItem(Header(3,_("HTML Unchanged.")))
         doc.AddItem('<hr>')
         return
-    code = cgi_info['html_code'].value
+    if Utils.GetCharset(mlist.preferred_language) == 'us-ascii':
+        # decoded values from TextArea may be 'iso-8859-1'
+        code = Utils.uquote(cgi_info['html_code'].value)
+    else:
+        code = cgi_info['html_code'].value
     if Utils.suspiciousHTML(code):
         doc.AddItem(Header(3,
            _("""The page you saved contains suspicious HTML that could