[utils] Fix unescapeHTML for misformed string like "&a"" (#13935)

ChangeLog

@@ -1,3 +1,9 @@
+version <unreleased>
+
+Core
+* [utils] Fix unescapeHTML for misformed string like "&a&quot;" (#13935)
+
+
 version 2017.08.18
 
 Core

test/test_utils.py

@@ -279,6 +279,7 @@ class TestUtil(unittest.TestCase):
         self.assertEqual(unescapeHTML('/'), '/')
         self.assertEqual(unescapeHTML('é'), 'é')
         self.assertEqual(unescapeHTML('�'), '�')
+        self.assertEqual(unescapeHTML('&a"'), '&a"')
         # HTML5 entities
         self.assertEqual(unescapeHTML('.''), '.\'')
 

youtube_dl/utils.py

@@ -596,7 +596,7 @@ def unescapeHTML(s):
     assert type(s) == compat_str
 
     return re.sub(
-        r'&([^;]+;)', lambda m: _htmlentity_transform(m.group(1)), s)
+        r'&([^&;]+;)', lambda m: _htmlentity_transform(m.group(1)), s)
 
 
 def get_subprocess_encoding():