Reporter NR Nandini
`PHP Event Calendar Multiple Parameter Cross Site Scripting Vulnerability
OS2A ID: OS2A_1007 Status:
08/20/2006 Issue Discovered
09/06/2006 Reported to the Vendor
09/09/2006 Fixed by Vendor
09/13/2006 Advisory Released
Class: Cross Site Scripting Severity: Low
PHP Event Calendar is a reusable PHP script that extends a web site's
functionality with an event scheduler and/or news archive.
A cross-site scripting vulnerability exists in PHP Event Calendar, due to input
validation error in parameters tilte(ti), body(bi) and backgroung Image(cbgi)
in cl_files/index.php page when adding a new event.
Successful exploitation requires authentication.
An authenticated remote attacker could inject malicious HTML and script code in
other user's browser session within the security context of the affected site.
PHP Event Calendar 1.5.1 (prior versions may also be vulnerable)
Proof of Concept:
Vulnerable fields: title field - ti
body field - bi
Backgroung Image - cbgi
Insert "<script>alert('XSS Vulnerable');</script>" in above field and click
CVSS Score Report:
ACCESS_VECTOR = REMOTE
ACCESS_COMPLEXITY = LOW
AUTHENTICATION = REQUIRED
CONFIDENTIALITY_IMPACT = NONE
INTEGRITY_IMPACT = PARTIAL
AVAILABILITY_IMPACT = NONE
IMPACT_BIAS = INTEGRITY
EXPLOITABILITY = PROOF_OF_CONCEPT
REMEDIATION_LEVEL = OFFICIAL_FIX
REPORT_CONFIDENCE = CONFIRMED
CVSS Base Score = 2.1 (AV:R/AC:L/Au:R/C:N/I:P/A:N/B:I)
CVSS Temporal Score = 1.6
Risk factor = Low
"Attached is the version that blocks the use of the <script> in the
text of the event. We can't block use of HTML completely because many
users want to be able to use HTML for the event descriptions. The
events are managed in the password protected control panel so there
was no security threat even before the change was applied."
Update to the fixed version,
NR Nandini of OS2A has been credited with the discovery of this vulnerability.