Differences with security implications (more!)

Dangerous platform defaults
AIX linker allowed loading for shared libraries from current directories
Portable OpenSSH did the right thing when using IBM's compiler
Got it wrong when using gcc instead

Sharing binaries between adjusted systems
Differences in limits, e.g. PATH_MAX, NGROUPS_MAX
Bang - buffer overflow

Some systems don't disable ptrace() after set[ug]id
