Hi Fakhri,
First of all – great plugin. Came in handy many times.
However one of my websites got hacked (sort of) recently. Weirdly the file system was clean but as I started digging it turned out that the SEO_404_links table was full of spammy links to some drug websites.
As a result Google picked up dozens of non-existent PDF’s which were in reality redirects to some dodgy websites.
I truncated the tables and removed the plugin (which solved the issue but still a long way before Google removes the “hacked” flag from search results) but the situation could indicated that there is indeed a vulnerability that allows such hacks.
I’d be happy to open a dialog with you about this potential issue.