CVE-2002-1894 in phpBB
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in viewtopic.php in phpBB 2.0.3 allows remote attackers to inject arbitrary web script or HTML via the highlight parameter.
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Analysis
by VulDB Data Team • 09/01/2025
The vulnerability identified as CVE-2002-1894 represents a classic cross-site scripting flaw in the phpBB bulletin board system version 2.0.3. This security weakness resides within the viewtopic.php script which processes and displays forum topics to users. The vulnerability specifically affects the handling of the highlight parameter, which is used to emphasize specific words or phrases within forum posts. The flaw allows remote attackers to inject malicious web scripts or HTML code through this parameter, potentially compromising user sessions and data integrity. This type of vulnerability falls under the category of CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security that enables attackers to inject malicious content into web pages viewed by other users.
The technical exploitation of this vulnerability occurs when phpBB fails to properly sanitize or escape user input received through the highlight parameter in the viewtopic.php script. When users browse forum topics and the system processes the highlight parameter, the application does not adequately validate or escape the input before rendering it in the web page output. This creates an environment where attackers can submit malicious payloads through the highlight parameter that get executed in the browsers of other forum users who view the affected topics. The vulnerability essentially allows attackers to inject script code that executes in the context of the victim's browser, potentially leading to session hijacking, credential theft, or other malicious activities. This attack vector aligns with the ATT&CK technique T1059.007 - Command and Scripting Interpreter: JavaScript, as it leverages JavaScript execution within web browsers to compromise user sessions.
The operational impact of CVE-2002-1894 extends beyond simple data corruption or theft, as it represents a significant threat to user trust and forum security. When exploited, this vulnerability enables attackers to manipulate forum content in real-time, potentially redirecting users to malicious websites, stealing session cookies, or even defacing the forum with malicious content. The widespread use of phpBB in online communities means that a successful exploitation could affect numerous users across multiple forums simultaneously. The vulnerability is particularly dangerous because it requires no special privileges or authentication to exploit, making it accessible to any remote attacker with knowledge of the forum's structure. The implications for forum administrators include potential data breaches, compromised user accounts, and damage to community trust. This vulnerability demonstrates the critical importance of input validation and output sanitization in web applications, as even seemingly benign features like text highlighting can become attack vectors when not properly secured.
Mitigation strategies for CVE-2002-1894 should focus on implementing proper input validation and output escaping mechanisms within the phpBB application. The most effective immediate solution involves updating to a patched version of phpBB 2.0.4 or later, as the vulnerability was addressed in subsequent releases. Organizations should also implement proper parameter sanitization techniques, including the use of HTML entity encoding for all user-supplied input before rendering it in web pages. Additional defensive measures include implementing content security policies to restrict script execution, using secure coding practices that prevent XSS vulnerabilities, and conducting regular security audits of web applications. The vulnerability highlights the necessity of following secure coding guidelines such as those outlined in the OWASP Top Ten, particularly focusing on input validation and output encoding as fundamental defenses against XSS attacks. Regular security updates and patch management processes are essential to protect against similar vulnerabilities that may arise in web applications, as this flaw demonstrates how a single unsanitized input parameter can create significant security risks for entire user communities.