diff --git a/Lib/cgitb.py b/Lib/cgitb.py
index 1c300b2..19b4149 100644
--- a/Lib/cgitb.py
+++ b/Lib/cgitb.py
@@ -183,7 +183,8 @@
 
 %s
 -->
-''' % ''.join(traceback.format_exception(etype, evalue, etb))
+''' % pydoc.html.escape(
+          ''.join(traceback.format_exception(etype, evalue, etb)))
 
 def text((etype, evalue, etb), context=5):
     """Return a plain text document describing a given traceback."""