Interesting issue: I have sites that have 2.8.2 and when attempting to update, TimThumb Scanner doesn't actually do it. Actually, it does: it installs 2.8.2:
Note that the first item, before the screenshot was taken, was 2.8.3 [as distributed by the WooThemes plugin, woo-tumblog]. When I ran "upgrade selected files" for both files, the 2.8.3 version went down to 2.8.2 and the 2.8.2 in the theme slidette, remained the same.
I deactivated and reactivated the script; no change. I even deinstalled and reinstalled, and no change. Using v1.43 of the scanner. I've noticed this issue on several sites I run. I also noticed that the Google Code depository shows that 2.8.5 is the latest version, not 2.8.4. Any tips you can provide would be most welcome! :)