diff -ur liborcus.org/include/orcus/sax_parser.hpp liborcus/include/orcus/sax_parser.hpp
--- liborcus.org/include/orcus/sax_parser.hpp	2013-12-13 20:51:55.126503773 +0100
+++ liborcus/include/orcus/sax_parser.hpp	2013-12-13 20:57:39.076174743 +0100
@@ -278,6 +278,8 @@
             special_tag();
         break;
         default:
+            if (!is_alpha(c))
+                throw malformed_xml_error("expect an alphabet.");
             element_open(pos);
     }
 }