CVE-2005-0872 in phpBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in calendar_scheduler.php in the Topic Calendar 1.0.1 module for phpBB allows remote attackers to inject arbitrary web script or HTML via the start parameter.
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Analysis
by VulDB Data Team • 12/23/2025
The vulnerability identified as CVE-2005-0872 represents a classic cross-site scripting flaw within the Topic Calendar 1.0.1 module for phpBB, a widely deployed forum software platform. This security weakness specifically affects the calendar_scheduler.php script which handles calendar-related functionality within the forum environment. The vulnerability stems from insufficient input validation and output sanitization mechanisms that fail to properly process user-supplied data before rendering it within web pages. Attackers can exploit this weakness by injecting malicious scripts or HTML content through the start parameter, which is typically used to define calendar event start times or dates. The affected module operates within the broader phpBB ecosystem where user-generated content flows through various processing layers before being displayed to other forum participants.
The technical implementation of this XSS vulnerability occurs when the calendar_scheduler.php script directly incorporates user input from the start parameter into HTML output without adequate sanitization or encoding. This allows malicious actors to craft specially formatted input that, when processed by the script, gets executed in the browsers of other forum users who view the affected calendar content. The vulnerability falls under CWE-79 which categorizes cross-site scripting as a code injection flaw where untrusted data is embedded into web pages viewed by other users. The attack vector operates through the standard HTTP request mechanism where an attacker can manipulate the start parameter to include script tags or other malicious HTML content that gets stored or immediately executed upon page rendering.
The operational impact of this vulnerability extends beyond simple script execution as it provides attackers with the capability to perform various malicious activities within the context of affected forum sessions. An attacker could potentially steal session cookies, redirect users to phishing sites, deface forum content, or execute more sophisticated attacks such as credential harvesting or privilege escalation within the forum environment. The vulnerability particularly affects phpBB installations running the Topic Calendar 1.0.1 module, creating a persistent security risk that could compromise the integrity of forum communications and user data. Given that phpBB forums often serve as community platforms for sensitive discussions, this vulnerability could enable attackers to access confidential information shared within these environments, making it a significant concern for organizations relying on these platforms for collaborative work or public communication.
Mitigation strategies for CVE-2005-0872 should focus on immediate input validation and output encoding measures to prevent malicious data from being processed as executable content. System administrators should implement proper parameter sanitization within the calendar_scheduler.php script by applying HTML entity encoding to all user-supplied data before rendering it in web pages. The recommended approach aligns with ATT&CK technique T1068 which addresses privilege escalation through web application vulnerabilities, emphasizing the need for robust input validation. Additionally, organizations should consider upgrading to newer versions of the Topic Calendar module or phpBB itself where these vulnerabilities have been addressed through proper security patches. Implementing content security policies and regular security audits of forum modules can help prevent similar issues from occurring in the future, while also providing defense-in-depth measures against other potential attack vectors targeting web applications.