Verified answer

if you sealed it properly there should be no problem, cereal dosent really go bad, it often goes soft. Ive eaten some really and i mean REALLY old cereal before, but was still pretty good since it was sealed properly.

Cereal On The Go

Because a bag in a box tends to not be sealed as good as a bag of chips w/ a chip clip.

You can still eat it, but it may be stale and have lost some of it's taste. If it still tastes alright, eat it.

Then it is probably bad