Solved in my case -> Firetray addon for thunderbird caused the blurry icon. https://addons.mozilla.org/nl/thunderbird/addon/firetray/
After loading thunderbird with firetray addon both firefox & thunderbird icons went blurry. After closing thunderbird they went normal. Disabling the addon fixed my issue.
Solved in my case -> Firetray addon for thunderbird caused the blurry icon. https:/ /addons. mozilla. org/nl/ thunderbird/ addon/firetray/
After loading thunderbird with firetray addon both firefox & thunderbird icons went blurry. After closing thunderbird they went normal. Disabling the addon fixed my issue.