"Extensions to Track" doesn't work and breaks tracking for Opera visitors

I noticed that downloads (jpg, jpeg, pdf, gif) and outgoing links were not being tracked — I tried various browsers and it was the same in them all. Tracking outgoing links was on so I’m not sure what is going on there, but I didn’t have any extensions listed. So I listed the above 4, but still no luck. Downloads were not being tracked (in any browser).

In the mean time, I noticed that tracking my own visits from Opera v12.12 (my main browser) had just stopped cold. But when they did get randomly tracked the only URL was detected was the one I was at if I logged in as a registered user, and even then it wouldn’t identify my name and would also preface the tracked URL of every page visited with the login URL (if that makes sense).

After much digging around (including eliminating all cookies, history and browser history — all to no avail) I eventually tracked the problem down to the ‘Extension to track” option. Just adding one (say “pdf”) was enough to break visitor tracking from Opera (Chrome 29.0.1547.66 m, IE 8.0 and FireFox 22 seem unaffected). Clearing the option restored everything back to normal.

http://wordpress.org/plugins/wp-slimstat/