For anyone looking for the patch: https://github.com/sektioneins/SUIDGuard
Edit: as noted in Esser's blog [1]: $ EDITOR=/usr/bin/true DYLD_PRINT_TO_FILE=/this_system_is_vulnerable crontab -e
I found this test failed in both a patched (10.10.4) and un-patched system (10.10.1) so not sure what these results mean.
[1] https://www.sektioneins.de/en/blog/15-07-07-dyld_print_to_fi...
$ ls -al /
(etc)
-rw-r--r-- 1 root wheel 0 Aug 6 06:46 this_system_is_vulnerable
So I can a) confirm the vulnerability exists and it can write with root privileges.and b) the patch works: I ran the patch, deleted the test file, rebooted and the file is no longer able to be written.