We are seeing it as well with 1.8.1:
192.168.24.45 - - [18/Aug/2015:16:28:41 +0000] "GET /MAAS/ws?csrftoken=5fERal3JfbELe3zJJEEc6uRobrilPsCS HTTP/1.1" 500 832 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:40.0) Gecko/20100101 Firefox/40.0"
We are seeing it as well with 1.8.1:
192.168.24.45 - - [18/Aug/ 2015:16: 28:41 +0000] "GET /MAAS/ws? csrftoken= 5fERal3JfbELe3z JJEEc6uRobrilPs CS HTTP/1.1" 500 832 "-" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:40.0) Gecko/20100101 Firefox/40.0"