I think it's using the icon for the dark theme. It's supposed to use the dark or light one
- Temporary Containers Version: 1.9.2
- Firefox Version: 115.9.1esr (64-bit)
Actual behavior
Icon is light on light background
Expected behavior
Icon should be dark on light background
Steps to reproduce
- set theme to "System theme -- auto"
- look at the tab bar icon
Notes
This is entirely solved by using either System theme light or dark explicitly. I assume the right color exists as a css variable with the firefox shell, but I have no experience inspecting that.