1. Install a brand new confluence 3.3.1
2. Go to Plugin Repository
3. Click the Upload tab
4. Browse to find a plugin file to upload. I tested with both the confluence-su plugin 1.2.1 and the adaptavist rate macro 3.0.
5. Click Upload

Expected Result Plugin uploaded and enabled

Actual Result

1. The screen says "Completed adding / updating 1 plugin(s)."
2. An IllegalArgumentException occurs and writes a stack trace to the atlassian-confluence.log
3. The plugin is listed in the PLUGINDATA table
4. There will be a copy of the jar in home/plugin-cache and home/temp
5. The plugin is not listed in the Plugin Repository page
6. The plugin is not enabled

This was a result of my testing from CSP-52394