Note: This does not affect Firefox 3.5 or 3.6 users!

Today I landed a patch for bug 551285, which removes support for certain parts of sessions created in Firefox 2.0 and 3.0. This means that if you upgrade directly from 2.0 or 3.0 to (currently 3.7), you will lose some session data.

The data you would lose is limited to the following:

  • Form data (2.0 and 3.0)
  • Session Cookies (2.0 only)
  • Tab XUL Attributes (2.0 and 3.0)
  • Session History Post Data (2.0 only)
  • Session History Owner (2.0 only)

If losing any of this data particularly bothers you, then it’s as simple as upgrading to Firefox 3.6 or Firefox 3.5 first. Alternatively, some session management add-ons could update your session file for you (for example, the author of Session Manager is updating his add-on to do that).