Checkbox checked state not updated correctly at www.democraticunderground.com

After clicking checkbox labeled "Remain logged in at this computer?" it's state doesn't change, url:
http://www.democraticunderground.com/?com=login

It's possible that it's just drawing issue, as adding "checked" attribute using Inspector also doesn't change it's state.
It seems to be Windows specific, I was unable to reproduce this using 5.2.1 and 5.3.0 on Kubuntu 14.04 64 bit.
It's reproducible using both Otter Browser and browser from Qt examples using Windows 7 32 bit.

Original bug report:
https://github.com/Emdek/otter/issues/314