Operating system: Windows 10
Graphics card: Sapphire Radeon RX Vega 64 Nitro+
Broken: 2.80 Release Candidate
Using the box hide tool in sculpting mode can't select multiple boxes to hide. Holding the left mouse to create a new selection to hide is considered as a click-and-release and basically reveal all hiden parts (which is the expected behaviour of click-and-release but not holding to create a new selection
Exact steps for others to reproduce the error
On default sculpting startup, select box hide tool, make a selection. Try to make a second selection with the tool and the previously hidden parts are revealed before the selection is made.