StepMania 5.0.12; release notes compiled and Markdown formatted by @kyzentun:

Player visible changes:

Gameplay

• Fixed bug that allowed pausing by pressing Select then Back. Pausing
  requires pressing the same button twice.
• Default theme ignores holding Back, Select, or Start during gameplay. The
  pause menu must be used to back out of a song.

Select Music

• Added AllowHoldForOptions preference. When this is set to 0 (off), going
  to the player options screen requires pressing Start a second time, instead
  of holding it.

Other

• Fixed bug that deleted a warp on the same beat as a stop when saving.
• Ready and Go announcer sounds no longer play simultaneously.
• Fixed crash in loading profiles from usb drives.

Themer visible changes:

• Bug fixes are marked with [B].
• Functions are marked with [F].
• Metrics added are marked with [M].

ScreenGameplay

• [M] UsePauseMenuInsteadOfGiveUp

ScreenSyncOverlay

• Actors are loaded from BGAnimations/ScreenSyncOverlay overlay instead of
  being hardcoded.

Pausing gameplay

Read Docs/Themerdocs/pause_menu.md for some explanation of handling pausing.