Auto Accept is a scam/hack in Animal Jam (and possibly in Animal Jam Play Wild). This is not confirmed to be a working hack currently, but it is possible that it may be used again. More commonly, people say they'll give you the hack to use on anyone in exchange for your user and password, which is a scam. This scam is similar to the Item Generator Scam.
There are a good amount of YouTube videos and websites advertising the hack, some of which have comments underneath saying that the hack worked. However, these comments are fake, as are most of the videos and sites.
Usually, people who have the actual hack look for people wanting offers for rare items (Headdresses, Rare Spikes, etc). The scammer will trade the person with a rare item a bad item, such as a necklace. Normally, the person being offered the bad item would decline the trade. However, the Auto Accept software the scammer is using force-accepts the trade, even if the person wanted to decline.
Every once in a while you may find a video about an Auto Accept website that needs your username and password to "work". The person who makes the video usually uses spare accounts, and all of the "force-accepted" trades are digitally created. If you believe the fake video, once you give the person with the "hack" your information, they can access your account and steal your rares.
How to avoid this hack/scam
Auto-Accept Hack: Avoid having good items on trade everywhere you go. However, having good items on trade is sometimes necessary. If you're offered a bad item for one of your good items, log off or press the X button instead of pressing the decline button. The decline button enables the hack, but logging off or pressing the X button has less of that risk.
Auto-Accept Scam: DO NOT TRY TO GET AN AUTO-ACCEPT HACK TO USE FOR YOURSELF. That is you wanting to scam and hack other players, which is dishonest and wrong. You may end up getting scammed yourself if you try to use the hack, and it serves you right for trying to scam other people.