Using Linux Mint 17.3 Rosa cinnamon.

I updated Firefox this morning, to FF53. Now I find that the text on most but not all buttons is blank, rather than being black text as it was in all earlier versions of FF.

For example the text on the Log In button for LinuxQuestions is blank. The two buttons below the edit box for this post are blank. So is the "x" on the active tab, so are other webpage buttons.

If I put my nose right up to the screen, shade my eyes with my hand, move my head around and peer at it for several seconds I can with great difficulty sometimes make out that the text is very faintly there. I use the "default theme" for Firefox, which is a pale grey classic style, and the lettering is very very very nearly the same colour.

So how can I return the lettering to being black again please?

Thanks.

is your desktop using a dark theme perchance?

No, as I write above, it is using the "Default" theme. I have tried switching to the "Compact Light" theme, but the buttons are still blank and thus unreadable.

I have gone to Preferences/themes in Linux Mint (not in Firefox) and changed "Controls" from "Adwaita" to "Mint-x grey", and that appears to have solved the problem. The text on buttons is now black and readable again.

I'm rather surprised that changing the OS theme should affect how webpage buttons in Firefox appear, but it did the trick.

certain parts (buttons, text fields etc.) are styled following the desktop's theme; not always, but often.
in my experience it has always been like that, at least for firefox-based browsers.

firefox has recently changed from being gtk2-based to gtk3-based, that might have brought some changes in appearance of said elements.

I have Firefox 52 using a dark GTK2 theme on my system. The menu style elements are different than previous versions. Looks the same with a GTK3 theme also. Hoping future versions will be dark-theme friendly again. For me, the main menu has dark icons, and white text on a light gray background. Right click menu still looks normal.

it's possible to start firefox with a specific gtk theme by specifying an env var. differs between gtk3 and gtk2, but something like