Steps to reproduce:

Create a new 3D URP project via Unity Hub
Select the PC_RPAsset.asset in the Project Browser
In the Inspector add the Exposure override and enable it for the Project
Add a lit object to the scene (e.g. a Cube) so the view has both lit geometry and empty/skybox background
In the Fixed Exposure field, enter a large negative value, e.g. -130 (any value past about -128) - the field accepts it with no clamping
Look at the Game view / Scene view

Actual results: The Fixed Exposure field is unclamped - it accepts any value with no minimum or maximum. Entering an extreme EV (past about -128) drives the exposure multiplier out of the float32 range: the CPU computes exposureMultiplier = Mathf.Pow(2, -fixedExposure), and 2^128 is already at FLT_MAX (~3.4e38), so any larger magnitude overflows to +Infinity. With an Infinity multiplier, lit (non-zero) pixels clip to white but truly-black pixels (0.0) become NaN via 0 * Infinity, so the skybox/black background stops rendering as white and appears black. The frame is left containing Infinity/NaN purely because the input value was never bounded.

Expected results: The Fixed Exposure value is clamped to a sane range so the field cannot be pushed into values that overflow the exposure multiplier to +Infinity or inject NaN into the frame. HDRP already clamps its exposure for exactly this reason; URP's Fixed Exposure should have the same guard. Out-of-range input should be limited (or the multiplier clamped to a finite maximum), not passed through to produce Infinity/NaN.

Reproducible with versions: 6000.7.0b1, 7000.0.0a1

Can’t test with versions: 6000.0.84f1, 6000.3.24f1, 6000.6.1f1 (No Fixed Exposure override in URP)

Tested on (OS): Windows 11

Notes:

Suggested fix: clamp fixedExposure to a sane EV range (as HDRP does), and/or clamp the computed multiplier to a finite maximum.