diff --git a/cookies.py b/cookies.py
index <HASH>..<HASH> 100644
--- a/cookies.py
+++ b/cookies.py
@@ -750,6 +750,11 @@ class Cookie(object):
             if key in ('name', 'value'): continue
             parser = cls.attribute_parsers.get(key)
             if not parser:
+                # Don't let totally unknown attributes pass silently
+                if not ignore_bad_attributes:
+                    raise InvalidCookieAttributeError(key, value,
+                        "unknown cookie attribute '%s'" % key)
+                _report_unknown_attribute(key)
                 continue
             parsed[key] = parse(key)
fix: don't let totally unknown attributes pass silently in from_dict

for example, if a dict supposedly representing a Cookie has an attribute 'duh' that is likely to indicate an error.
if the user set ignore_bad_attributes=False they want an exception. even if it's true, the typical behavior elsewhere is to log unknown attribute.