I ues Alfred for a long time, but this weird problem occurred today.
When I fired Alfred after I start my computer today, I found the theme was not the one I used, so I went to the setting panel then found every custom theme disappeared. I use Dropbox for backing up, it shows that two prefs.plist were modified couple minutes ago. Those two files were located in /Alfred.alfredpreferences/preferences/appearance and /Alfred.alfredpreferences/preferences/features/websearch, so all custom web search were gone, I don't even know who did this!
The weird thing came up, I restored the old prefs