That was a nasty bug! But not anymore. Try it this time.
Following KiwiForum 1, we have the source code of this challenge, but this time the bug on loader is patched. We were at the Milan Codemotion 2015 on our second day, so we coded this hack while moving to different speakers every hour or so.
Using the header HTTP_RANGE available by the downloader, we wrote a php script to download intervals of the image. Doing so, we played with the function generate_bitmap($width,$height,$bitmap) in the purecaptcha.php file.
After a few minutes, here is the result:
Due to a bug in the script, (my fault!) the first characters in the first two lines are actually at the end.
The flag so it becomes: 0390c17ec34f1b4c