Facebook recently added a new feature to its mobile apps in which it opens links in an in-app browser instead of your default. This is faster, but if you like the sharing options, bookmarks and anything else you've customised about your preferred browser, you can disable this behaviour.
If you disable it, the Facebook links will open in your default browser instead:
- In the Facebook app, go to Menu > App Settings.
- Tap to turn on the "Always open links with external browsers" option.
Facebook's in-app browser isn't bad. It just doesn't have as many sharing options as the one you probably use for everything else, and it certainly doesn't have any other add-ons or customisations you've made to personalise your browsing experience.