I've tried uninstalling and reinstalling Firefox several times and tried updating my Flash player. I don't believe I have automatic updates enabled, and I didn't update Firefox myself, so I have no clues as to why it started acting like this. The strange thing is this happened out of the blue, in the middle of the day when I had used Firefox without issue. Long story short, the program is laggy and sluggish. When attempting to open the in-browser settings menu or anything from the top bar (File, Edit, History, etc.), the button highlights and gets stuck there, and the menu never actually opens. Accessing sites is possible, but similarly sluggish, with every action taking ~10-15 seconds before even beginning to load. Clicking the address bar, the text cursor doesn't blink, and if I start to type an address, it only populates two letters at a time before lagging for ~10 seconds and populating the next two. After a few seconds, only some of the add-on icons and the leftmost bookmark bar item will appear, and then nothing else. When I open a new window, the top bars appears mostly blank, lacking any of the bookmarks bar items or add-on icons. About four days ago, I opened Firefox to check my email to find that the program acting extremely sluggish.

Macos virtualbox laggy