Never brag about anything you've shoplifted, on the internet or in real life. Why? If you brag about it in real life to someone you trust, they might not be as trustworthy as you think, and could end up reporting you to the police. Or, if you later have a falling out with them, they could decide to report you out of revenge. Or, they could pass your story on to other people, and whoever hears it next could decide to report you.
If you brag about it on the internet, it could be used to de-anonymize you. If you say, "I just stole items A, B, C, and D from store E," and those are an uncommon combination of items, then there's a pretty low chance that more than one person stole that exact combination of items from that certain store on that one day. A police officer who happened to stumble across your post would know that your online identity is the one who stole those items. If they were able to determine who you are in real life (say, through facial recognition from security camera footage), then, besides you having a warrant placed for your arrest, your online identity would then be linked to your real identity, so you'd be de-anonymized. Or, if your online identity is ever linked to your real identity (de-anonymized) in the future, and you bragged about shoplifting online, but you were never caught in real life, then the police would be able to figure out that you shoplifted, since you bragged about it online (anonymously, at the time).
TL;DR: If you successfully shoplift something, never tell anyone else, no matter how badly you want to. Take the secret with you to your grave.
This doesn't just apply to shoplifting - it applies to doing anything illegal. Loose lips sink ships.