The "Go to Last Post" button is not functioning properly in Firefox after a recent upgrade, affecting users across multiple platforms. Many users report that clicking the button leads them to the beginning of threads instead of the last post. The issue appears to stem from changes in VB 3.6.x, where the "goto=lastpost" command no longer operates as expected. Some users suggest using the Prime skin for updated templates as a potential workaround. Overall, the problem persists for several users, indicating a widespread issue with the button's functionality.