It just goes to show that all project owners should be responsible for turning on maximum compiler warnings which make sense for their project. There are lots of great gcc warnings/errors which are not enabled by default. In particular, this one is reported by -Wformat-nonliteral or -Wformat-security. From the gcc docs:

  -Wformat is included in -Wall. For more control over some 
  aspects of format checking, the options -Wformat-y2k,
  -Wno-format-extra-args, -Wno-format-zero-length,
  -Wformat-nonliteral, -Wformat-security, and -Wformat=2
  are available, but are not included in -Wall.