Earlier in the week we discovered a number of places in VaultWiki where fatal or database errors would be encountered under relatively common circumstances. We also discovered what could be a major issue in versions dating back to 2.5.0.
Stability in 2.5.x
Starting with VaultWiki 2.5, the Island namespace was moved to the database. However, because of the way the ID was stored, and an inconsistency in how the record was created, it wasn't uncommon for the namespace to disappear entirely.When the Island namespace disappears, it can have serious implications on the rest of the wiki. It's possible that many articles will no longer be visible, and the usual fix of rebuilding namespaces has no effect in this case.
Even though 2.5.7 was the last "stable" release, this problem is now fixed in 3.0.0 Beta 6, making it, we believe, more stable than 2.5.7. If you aren't experiencing problems like that mentioned above in 2.5.7, you should feel safe sticking with that version until now. Otherwise, we recommend upgrading as soon as you are able.