Hi @OJSUSER11,
As far as we’re aware, OJS 2.4.x is secure to run; can you clarify the security problem you mention?
Are you sure you’re running the upgrade on a clean copy of your 2.x database? If you try an upgrade and it fails, you’ll need to restore from backup. Make sure to fully drop and re-create the database as part of this process.
Regards,
Alec Smecher
Public Knowledge Project Team