Flash upload removed - Security Issue
A security issue has been discovered in the YUI libraray. The issue in question affects the Flash Uploader in Vbulletin Forums. Yahoo (The developer of Yahoo) has stated that there will be no patch for this security issue due to the product having reached its "end of life" ie is no longer supported.
To prevent any problems arising from this issue the flash uploader has been disabled and replaced with a Java script based uploader. Everything will work similar to before but you will notice that things look a little bit different when you upload files.
Read more about the bug here: http://yuilibrary.com/support/20131111-vulnerability/
Do as I say. Not as I do.