CVE-2020-16193 in osTicket
Summary
by MITRE
osTicket before 1.14.3 allows XSS because include/staff/banrule.inc.php has an unvalidated echo $info['notes'] call.
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Analysis
by VulDB Data Team • 11/11/2020
The vulnerability identified as CVE-2020-16193 represents a cross-site scripting flaw in the osTicket help desk software affecting versions prior to 1.14.3. This issue stems from improper input validation within the staff ban rule functionality where user-supplied data is directly echoed without appropriate sanitization. The affected file include/staff/banrule.inc.php contains a code pattern that outputs the $info['notes'] variable without filtering or encoding potentially malicious content. This creates an avenue for attackers to inject malicious scripts into the application's user interface through the notes field of ban rules. The vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically representing a stored XSS variant where malicious payloads persist in the application's database and execute whenever the affected page is loaded. The flaw enables attackers to execute arbitrary JavaScript code within the context of other users' browsers, potentially leading to session hijacking, credential theft, or further exploitation of the compromised user accounts.
The operational impact of this vulnerability extends beyond simple script execution as it compromises the integrity and security of the entire help desk system. When authenticated staff members view the ban rule notes section, their browsers execute the injected malicious code, creating a persistent threat vector that can be leveraged for privilege escalation or data exfiltration. Attackers could craft payloads that steal session cookies, redirect users to malicious sites, or manipulate the application interface to hide malicious activities. The vulnerability is particularly dangerous in shared environments where multiple staff members access the same administrative interface, as a single compromised note field could affect numerous users. According to ATT&CK framework, this vulnerability maps to T1059.007 for Scripting and T1531 for Account Access Removal, as it enables attackers to establish persistent access through session manipulation and potentially compromise administrative accounts.
Mitigation strategies for CVE-2020-16193 require immediate implementation of the official patch released by osTicket developers for version 1.14.3 and subsequent releases. Organizations should implement input validation and output encoding mechanisms that sanitize all user-supplied data before rendering it in the application interface. The fix should employ proper HTML entity encoding for all dynamic content, particularly in administrative sections where users can input free-form text. Security teams should also implement web application firewall rules to detect and block known XSS patterns in request parameters and form data. Regular security assessments should include testing for similar vulnerabilities in other parts of the application where user input is processed without proper sanitization. Additionally, implementing Content Security Policy headers can provide an additional layer of protection against XSS attacks by restricting script execution from unauthorized sources. Organizations should conduct thorough security training for administrators to recognize potential XSS attack vectors and maintain up-to-date security monitoring to detect unusual activities in the help desk system.