OS: Microsoft Windows 10 Professional 10.0.19045 Build 19045
Adobe Illustrator: 28.1 (64-bit)

Steps to reproduce the bug:
- Create a blank Illustrator document.
- Create a new shape, such as a white circle with no stroke. The white circle on the white background is invisible.
- Add an outer glow effect to the circle, e.g.: Color: black (#000000), Normal mode, 20% Opacity, 3px Blur.
=> The white circle on white background will be almost invisible, despite the black glow, which is very, very faint.

• Export the artwork to PDF.
• Open the PDF file in Acrobat : the white circle is perfectly visible, the black glow can be clearly seen.

Expected result:
The glow should look the same in Illustrator and Acrobat.

Actual result:
The glow looks too light in Illustrator, and is rendered properly in Acrobat.

If you set the glow's opacity to ~50% in AI, you will get in Illustrator the same rendering as 20% in Acrobat (but then of course, if you export the AI file to PDF, the 50% setting will appear much darker in Acrobat).

This bug is obviously linked to a recent AI update. The rendering used to be consistent between AI & Acrobat.

Attached:
- Screenshot (.png) of the same elements in Adobe Illustrator (left) and in Acrobat.
(unable to post AI & PDF sample files: blocks the post)