It fixes a minor security issue (local DOS attack) that only affects Fedora 12. Fedora 13 has already been updated and Fedora 11 and Fedora 10 doesn't have this issue since it was newly introduced in a later version.

aria2-1.6.2 Release Notes:

This release fixes segmentation fault error if URI to download
contains printf format string and logging is enabled.

• Fixed the bug that causes segmentation fault if
  req->getCurrentUrl() contains printf format string such as %d. The
  statement that causes this bug is useless and removed.

References:

http://aria2.svn.sourceforge.net/viewvc/aria2/trunk/NEWS?revision=1586