An issue was discovered in Icinga 2.x through 2.8.1. The daemon creates an icinga2.pid file after dropping privileges to a non-root account, which might allow local users to kill arbitrary processes by leveraging access to this non-root account for icinga2.pid modification before a root script executes a "kill `cat /pathname/icinga2.pid`" command, as demonstrated by icinga2.init.d.cmake.
etc/initsystem/prepare-dirs in Icinga 2.x through 2.8.1 has a chown call for a filename in a user-writable directory, which allows local users to gain privileges by leveraging access to the $ICINGA2_USER account for creation of a link.