text in certain languages rendered as boxes

Text in certain languages is rendered as boxes. If I copy this text and paste it in other applications/see the clipboard, the text is perfectly visible over there. Also, if I turn off advanced protection the text becomes visible on Firefox. This wasn't the case earlier, keeping advanced protection on would still render text. Happening since long, so don't have track for version history and when started to happen. Firefox (general release) on Android. Tried on other devices too, was able to replicate, thus not device specific.