Every time I try to post a question or answer, my browser pops up a confirmation dialog:
I need to choose "leave page" to continue. If I chose "stay on this page" and hit "submit" again, I am told that my post is a duplicate. In other words, the post was successfully submitted the first time, before the confirmation dialog.
I can confirm this by opening the page in a new tab and I can see my answer there despite being told that I haven't actually posted it. This happens on both firefox (40.0 and previous versions) and chromium (45.0.2454.85) and on all sites of the network.
Both browsers running on a 64 bit Debian. This may or may not be related to this other bug.
This is what I see in the Network tab of chromium's dev tools when submitting:
and after clicking on "leave page":
I just checked and this doesn't occur with another account on the same machine, which would suggest that it is somehow a problem on my end. Any ideas what could cause this? It can't be an extension issue since it occurs in both firefox and chromium. What would those two share that could produce this issue?