While getting your tightly held secrets spilled by tech-savvy fans digging through your game files is extremely bothersome, it is also inevitable. Letting something slip on your own however must be a tad embarrassing.
With the week-long GTA Online event celebrating the recent release of Lowriders: Custom Classics having ended yesterday, we can expect the next event to be announced soon, seeing as in recent months Rockstar has been holding these things back to back.

However the focus of the next event may have been spoiled ahead of schedule — and no data-miners were involved this time around. Knowing how running online games works, one will also know that even minute changes like an event in GTA Online needs to be properly set up behind the scenes and much of the data is pre-loaded secretly well in advance.
In such a case the pre-loaded data has the possibility of popping up in the live version due to bugs or human error. That is what seemingly happened in this case, where a PS4 user reported on some strange, unannounced changes having been made to GTA Online.
Reddit user and GTA V fan Clipper_Murray posted that he witnessed all visual and performance upgrades at Los Santos Customs being discounted suddenly and that his character received an exclusive shirt with the caption "The Shoulders Of Orion II".