While it doesn’t appear to include any major or important changes, Firefox 87 will apparently be the first update to the popular web browser used by default on numerous GNU/Linux distributions to disable the Backspace key from working as a back button when you want to navigate back to the previous page.
This change was supposed to land in the Firefox 86 release that arrived earlier today, but, for some reason unknown to me, it didn’t happen, and it looks like Mozilla delayed it for Firefox 87. Mozilla recommends that you use the Alt + Left arrow keyboard shortcut instead.