How to reproduce:
1. Download attached the project file
2. Either build a new exe or use the existing Test.exe
3. Run chosen .exe
4. Open OBS (https://obsproject.com/) and create a new 'Game Capture Source' under "Sources"
4.1. Name of the source doesn't matter
4.2 Set 'Mode' to "Capture specific Window"
4.3 Set Window to "[Test.exe] Check"
4.4 Toggle 'Allow Transparency' to "True"
4.5 Select 'OK'
5. Compare differences

Actual result: The built app works as intended when in consideration of Unity alone, however, when other programs attempt to capture the application whilst utilizing the alpha channel of the frame buffer, the result winds up incorrect. The alpha is more prominently incorrect in the post-processing, but other shaders are affected as well.

Reproduced with: 2017.3.1p3, 2018.1.0b10, 2018.2.0a3