Here are the details from the Slackware 13.1 ChangeLog:
+--------------------------+
patches/packages/rdesktop-1.6.0-i486-2_slack13.1.txz: Rebuilt.
Patched a traversal vulnerability (disallow /.. requests).
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-1595
(* Security fix *)
+--------------------------+


Where to find the new packages:
+-----------------------------+

HINT: Getting slow download speeds from ftp.slackware.com?
Give slackware.osuosl.org a try. This is another primary FTP site
for Slackware that can be considerably faster than downloading
directly from ftp.slackware.com.

Thanks to the friendly folks at the OSU Open Source Lab
(http://osuosl.org) for donating additional FTP and rsync hosting
to the Slackware project! :-)

Also see the "Get Slack" section on http://slackware.com for
additional mirror sites near you.

Updated package for Slackware 11.0:
ftp://ftp.slackware.com/pub/slackware/slackware-11.0/patches/packages/rdesktop-1.6.0-i486-2_slack11.0.tgz

Updated package for Slackware 12.0:
ftp://ftp.slackware.com/pub/slackware/slackware-12.0/patches/packages/rdesktop-1.6.0-i486-2_slack12.0.tgz

Updated package for Slackware 12.1:
ftp://ftp.slackware.com/pub/slackware/slackware-12.1/patches/packages/rdesktop-1.6.0-i486-2_slack12.1.tgz

Updated package for Slackware 12.2:
ftp://ftp.slackware.com/pub/slackware/slackware-12.2/patches/packages/rdesktop-1.6.0-i486-2_slack12.2.tgz

Updated package for Slackware 13.0:
ftp://ftp.slackware.com/pub/slackware/slackware-13.0/patches/packages/rdesktop-1.6.0-i486-2_slack13.0.txz

Updated package for Slackware x86_64 13.0:
ftp://ftp.slackware.com/pub/slackware/slackware64-13.0/patches/packages/rdesktop-1.6.0-x86_64-2_slack13.0.txz

Updated package for Slackware 13.1:
ftp://ftp.slackware.com/pub/slackware/slackware-13.1/patches/packages/rdesktop-1.6.0-i486-2_slack13.1.txz

Updated package for Slackware x86_64 13.1:
ftp://ftp.slackware.com/pub/slackware/slackware64-13.1/patches/packages/rdesktop-1.6.0-x86_64-2_slack13.1.txz

Updated package for Slackware -current:
ftp://ftp.slackware.com/pub/slackware/slackware-current/slackware/xap/rdesktop-1.6.0-i486-2.txz

Updated package for Slackware x86_64 -current:
ftp://ftp.slackware.com/pub/slackware/slackware64-current/slackware64/xap/rdesktop-1.6.0-x86_64-2.txz


MD5 signatures:
+-------------+

Slackware 11.0 package:
38e5ac5c9c7f026d28c261639b823f5e rdesktop-1.6.0-i486-2_slack11.0.tgz

Slackware 12.0 package:
22fa31babfd7d91158e80bd0f1badf43 rdesktop-1.6.0-i486-2_slack12.0.tgz

Slackware 12.1 package:
f17d588243b3ec3921de3b7e4cf790ff rdesktop-1.6.0-i486-2_slack12.1.tgz

Slackware 12.2 package:
312d0969d23b349f3b424d49825176be rdesktop-1.6.0-i486-2_slack12.2.tgz

Slackware 13.0 package:
88411f9f9f95518c498b2039c9a15a81 rdesktop-1.6.0-i486-2_slack13.0.txz

Slackware x86_64 13.0 package:
e0228d49d403ba9bcd33ad06dba11794 rdesktop-1.6.0-x86_64-2_slack13.0.txz

Slackware 13.1 package:
56dcdce7c80d9b3abfd2247a429b8dbd rdesktop-1.6.0-i486-2_slack13.1.txz

Slackware x86_64 13.1 package:
723edd12f7cc7b929ae5e5a5ae4f91de rdesktop-1.6.0-x86_64-2_slack13.1.txz

Slackware -current package:
5e30e1e9ea0b73d3ed3c4e147bcb2b01 xap/rdesktop-1.6.0-i486-2.txz

Slackware x86_64 -current package:
afce9228bef5941881ee991ca61033be xap/rdesktop-1.6.0-x86_64-2.txz


Installation instructions:
+------------------------+

Upgrade the package as root:
# upgradepkg rdesktop-1.6.0-i486-2_slack13.1.txz


+-----+

Slackware Linux Security Team
http://slackware.com/gpg-key