APC UPS daemon, apcupsd, saves its process ID in a world-writable file, which allows local users to kill an arbitrary process by specifying the target process ID in the apcupsd.pid file.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5654
https://euvd.enisa.europa.eu/vulnerability/EUVD-2001-0040
http://www.securityfocus.com/bid/2070
http://www.linux-mandrake.com/en/security/MDKSA-2000-077.php3
http://archives.neohapsis.com/archives/bugtraq/2000-12/0066.html