-------------------------------- | GuppY makes XSS attacks easy | -------------------------------- PROGRAM: GuppY VULNERABLE VERSIONS: All versions under 2.4p1 IMMUNE VERSIONS: 2.4p1 SEVERITY: high Tested version ============== GuppY 2.4 on the official GuppY website. Description ============ "GuppY is a small web portal, meant to be easy to use for the end user that you are, and which does not require a database to run.This architecture allows then to install it on almost all Internet web sites hosters (or almost all of them), the only preriquisite being that your hoster has to provide the PHP scripting language facility." - GuppY website GuppY use the postguest.php file for its forum and guestbook modules. This file contain XSS holes, an attacker can execute code since [c=codecolor]text[/c] has no filter. POSTGUEST.PHP ============= Problems come from this part: Line 196: $ptxt = preg_replace("/(\[c=(.*?)\])(.*?)(\[\/c\])/i", "\\3",$ptxt); Line 197: $ptxt = preg_replace("/(\[c=(.*?)\])(.*?)(\[\/C\])/i", "\\3",$ptxt); Line 198: $ptxt = preg_replace("/(\[C=(.*?)\])(.*?)(\[\/c\])/i", "\\3",$ptxt); Line 199: $ptxt = preg_replace("/(\[C=(.*?)\])(.*?)(\[\/C\])/i", "\\3",$ptxt); A badly disposed member can post a message containing code really easily in forum and guestbook modules. Example: (This proof-of-concept will show a window that can freeze your computer if using Internet Explorer so take care) [c=expression(alert('unsecure'))]texte[/c] Solution ======== In order to avoid the vulnerability, add a filter that will block ;<>*()"'] caracters to lines 196 to 199: Line 196: $ptxt = preg_replace("/(\[c=([#a-zA-Z0-9]*)\])(.*?)(\[\/c\])/i", "\\3",$ptxt); Line 197: $ptxt = preg_replace("/(\[c=([#a-zA-Z0-9]*)\])(.*?)(\[\/C\])/i", "\\3",$ptxt); Line 198: $ptxt = preg_replace("/(\[C=([#a-zA-Z0-9]*)\])(.*?)(\[\/c\])/i", "\\3",$ptxt); Line 199: $ptxt = preg_replace("/(\[C=([#a-zA-Z0-9]*)\])(.*?)(\[\/C\])/i", "\\3",$ptxt); Vendor status ============== GuppY developper's team has been contacted, a patch has been released tonight that fix the problem. Thanks to aldweb (freeguppy.org webmaster) for his quick answer. Links ===== GuppY: http://www.freeguppy.org Patch: http://www.freeguppy.org/file/guppy_patch2.zip Version 2.4p1: http://www.freeguppy.org/file/guppy.zip This vulnerability's orginal paper can be found here: http://www.echu.org/articles/alertes/echu-alert4.txt David Suzanne (dAs) das[a]echu.org http://www.echu.org ----------------------------------------------------------------- ECHU.ORG is not responsible for the misuse of the information we provide through our security advisories. These advisories are a service to the professional security community. In no event shall ECHU.ORG be liable for any consequences whatsoever arising out of or in connection with the use or spread of this information. -----------------------------------------------------------------