arc 5.21j and earlier create temporary files with world-readable permissions, which allows local users to read sensitive information from files created by (1) arc (arc.c) or (2) marc (marc.c).
http://www.zataz.net/adviso/arc-09052005.txt
http://www.debian.org/security/2005/dsa-843
http://secunia.com/advisories/17068