CVE-2002-0739 in PostCalendar
Summary
by MITRE
Cross-site scripting in PostCalendar 3.02 allows remote attackers to insert arbitrary HTML and script, and steal cookies, by modifying a calendar entry in its preview page.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/04/2019
The vulnerability identified as CVE-2002-0739 represents a critical cross-site scripting flaw within PostCalendar 3.02, a web-based calendar application that was widely used in the early 2000s for managing and displaying calendar events. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a fundamental web application security weakness that allows attackers to inject malicious client-side scripts into web pages viewed by other users. The specific implementation flaw occurs within the preview functionality of the calendar application where user input is not properly sanitized or escaped before being rendered back to the browser.
The technical exploitation of this vulnerability occurs when remote attackers manipulate calendar entries through the preview page feature, enabling them to inject arbitrary HTML and JavaScript code directly into the application's output. This injection capability stems from insufficient input validation and output encoding mechanisms within the PostCalendar application's rendering pipeline. When users view calendar entries that contain malicious script code, the browser executes this code in the context of the victim's session, potentially allowing attackers to perform actions with the victim's privileges. The vulnerability specifically targets the preview functionality, which serves as a staging area for calendar entries before they are permanently saved, making it a particularly dangerous attack vector since users often preview entries before finalizing them.
The operational impact of this vulnerability extends beyond simple script execution to include session hijacking and credential theft through cookie manipulation. Attackers can craft malicious calendar entries that, when previewed by authenticated users, steal session cookies or other sensitive information stored in the browser's memory. This capability enables unauthorized access to user accounts and potential privilege escalation within the calendar application's user management system. The vulnerability also represents a significant threat to the confidentiality and integrity of calendar data, as attackers can modify or exfiltrate information through the injected scripts. Additionally, the attack can be amplified through social engineering techniques where users are tricked into previewing malicious calendar entries, making this a particularly insidious vulnerability that combines technical exploitation with human factors.
Organizations and security practitioners should implement multiple layers of mitigation strategies to address this vulnerability effectively. The primary remediation involves upgrading to a patched version of PostCalendar that properly sanitizes user input and implements proper output encoding for all dynamic content. Input validation should be strengthened to reject or escape potentially dangerous characters and script tags before processing user-entered data. The application should implement Content Security Policy headers to prevent execution of unauthorized scripts, and all user-generated content should be properly escaped when rendered in HTML contexts. This vulnerability aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments or links, and T1071.001 for application layer protocol usage. Organizations should also conduct regular security assessments of web applications to identify similar input validation flaws and implement comprehensive logging to detect suspicious calendar entry modifications that might indicate exploitation attempts.