No Small Text

Z 1 z 5 gwězdkow pógódnośony

wót Wužywaŕ Firefox 1384f3 dnja Jan. 8, 2018 · trajny wótkaz

I don't know where this add on came from but suddenly my font in my thunderbird email is miniscule?? The program does not work in my updated version of firefox. I can't find how to even remove this add on. Please advise as this is my work computer and I am straining to read my emails. It doesn't see to have affected my web pages?