What's this thing sometimes added to the URL?

[Night Fox]

every once in a while, the forum gets this 404 error, and some extra characters are added in

so it's like
http://forum.blockland.us/QNSfW/index.php
but I don't add it myself or anything, it just appears there
and if I refresh the page it just gives me more 404 errors until I delete the added part from the URL

soo, what's up with that? it's just started happening this morning

[Ad Bot]

[LeetZero]

I shouldven't have locked http://forum.blockland.us/index.php?topic=251155.0 then.
This also happened to me there on the image. Specifically the hot poll image, the link received those extra characters. But the pages loaded fine.
Didn't even notice the extra letters at the time.

[Isjix]

what browsers are you guys using?
if any addons, what are they? I've never had it happen

[Night Fox]

what browsers are you guys using?
if any addons, what are they? I've never had it happen

it just started happening this morning, I hadn't installed anything so that's not an option
but it isn't doing it anymore, as far as I can tell