Hi!
I just checked with a fresh 15.10.7-SNAPSHOT default flavor distribution, and I could not reproduce your bug. As far as I know, the text color inside the boxes should be dark.
I searched it down, and they come from the @state-success-text
bootstrap variables. Those should be set up by default in bootstrap itself, as far as I could see XWiki default flavor doesn’t manipulate them.
Starting in cycle 15, we try to provide better accessibility for XWiki, and one of those aspect is to update colors to ensure enough contrast on all elements. As a rule of thumb, the new defaults (in the Iceberg colorhteme at least) most of the time use dark font color on a light background.
Here, the font color is anomalous.
I can’t really help you more with the info you provided so far. I think this comes from a customization in a SSX or your color theme advanced section.
Let me know how it goes
Have a good day!
Lucas C.