System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.87

Blender Version
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-10-12 22:51, hash: rBdc71ad062408

Short description of error
I am aware that there was a somewhat recent bugfix to the way Eevee handles bloom + transparency (I couldn't find the commit, but I'll edit this post when I find it). In the latest experimental builds the problem seems to be fixed, however when I go to save the image the output is still broken, and looks the same as if I rendered it out of 2.90.

2.90 render (saved, and when in image editor)

2.91 render (saved with 'as render' checked)

2.91 render (saved with 'as render' not checked)

2.91 screenshot of the render in the image editor displaying correct behavior.

Exact steps for others to reproduce the error

1. Add object with bright emissive material
2. Turn on bloom
3. Render
4. Save image

Here's the test file I was using