The bug

If the player's value for "XpP" is much higher than is normally attainable, parts of the GUI texture atlas can be displayed on screen.

As of 1.20.2 (23w31a), seeing the effects of this requires resizing the game window. In 1.20.1 and earlier, the effects are visible without resizing, manifesting as a duplicated XP bar. I believe this issue goes back to around the time when XP was implemented - attached are screenshots taken as far back as 1.0.0.

How to reproduce

1. Download the attached world file
2. Load it up
3. Resize your window to be short and wide

Expected results

On the far right of the screen, a conglomeration of UI element textures would not be visible.

Actual results

They are.