CVE-2006-3568 in Fantastic Guestbook
Summary
by MITRE
Multiple cross-site scripting (XSS) vulnerabilities in guestbook.php in Fantastic Guestbook 2.0.1, and possibly earlier versions, allow remote attackers to inject arbitrary web script or HTML via the (1) first_name, (2) last_name, or (3) nickname parameters.
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Analysis
by VulDB Data Team • 10/20/2025
The vulnerability identified as CVE-2006-3568 represents a critical cross-site scripting weakness in the Fantastic Guestbook 2.0.1 web application, with potential implications for earlier versions of the software. This vulnerability resides within the guestbook.php script which processes user input through three specific parameters: first_name, last_name, and nickname. The flaw stems from inadequate input validation and output encoding mechanisms that fail to properly sanitize user-supplied data before it is rendered back to other users within the guestbook interface. This type of vulnerability falls under CWE-79 which specifically addresses improper neutralization of input during web page generation, making it a classic example of client-side code injection that can be exploited by malicious actors to execute unauthorized scripts in the context of other users' browsers.
The operational impact of this vulnerability extends beyond simple data corruption or display issues, as it provides attackers with the capability to hijack user sessions, steal sensitive information, or redirect victims to malicious websites. When users submit entries containing malicious script code through the vulnerable parameters, this code gets stored in the guestbook database and subsequently executed whenever other users view the guestbook page. The attack vector is particularly concerning because it requires no privileged access or authentication, making it accessible to anyone who can submit data to the guestbook. This aligns with ATT&CK technique T1531 which describes the use of malicious scripts to gain access to user sessions and compromise web applications.
The technical exploitation of this vulnerability demonstrates how insufficient sanitization of user input can create persistent security risks within web applications. The vulnerability exists because the application fails to implement proper input validation techniques such as whitelisting acceptable character sets or implementing comprehensive output encoding before rendering user data. This weakness allows attackers to inject script tags or other malicious content that can execute in the context of other users browsing the guestbook. The vulnerability affects the entire user base of the application since any stored malicious content becomes active whenever the guestbook is accessed, creating a potential for widespread compromise of user data and browser sessions.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and output encoding mechanisms. The most effective approach involves sanitizing all user input through proper validation before storing it in the database, and ensuring that any data rendered to web pages undergoes appropriate encoding to prevent script execution. This includes implementing proper HTML escaping for all output, utilizing parameterized queries where applicable, and establishing a comprehensive input validation framework that rejects potentially malicious content. Organizations should also consider implementing content security policies to further reduce the impact of successful XSS attacks. The remediation process requires updating the guestbook.php script to properly handle user input through established security practices such as those outlined in the OWASP Top Ten and secure coding guidelines. Additionally, regular security assessments and code reviews should be implemented to identify similar vulnerabilities in other components of the web application.