Reproduction steps:
1. Download the attached project: "InputSystemMousePositionBug.zip"
2. Open the SampleScene
3. Enter the Play Mode
4. Select the "NewBehaviourScript" GameObject in the Hierarchy
5. Move the mouse cursor outside the left side of the Game view
6. Observe the X value in the Inspector

Expected result: The X value of the mouse cursor goes into negative values
Actual result: The X value does not go into negative values

Reproducible with: Input System 1.0.2 - 1.1.0-preview.3 (2019.4.22f1, 2020.2.7f1, 2020.3.0f1, 2021.1.0b11, 2021.2.0a8)
Could not test with: 2018.4.33f1 (Newest versions of Input System are not available)

Notes:
- Tested on Ubuntu 18.04
- Not reproducible on Windows and macOS
- Mouse.WarpCursorPosition may also be affected by this. The user reported that in their tests it seemed to randomly pick a Unity panel and warp accordingly to it.