CVE-2023-51317 identifies a multiple HTML injection vulnerability in PHPJabbers Restaurant Booking System version 3.0. The affected parameters include 'name', 'plugin_sms_api_key', 'plugin_sms_country_code', and 'title'. HTML injection vulnerabilities occur when user-supplied input is not properly sanitized or encoded before being included in web pages, allowing attackers to inject arbitrary HTML content. This can lead to various attacks such as cross-site scripting (XSS), content spoofing, or UI redressing. In this case, the injection points allow an unauthenticated attacker to remotely submit crafted input that is rendered by the application without proper sanitization. The CVSS v3.1 base score is 6.5, indicating a medium severity level, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and impacts on confidentiality and integrity but not availability (C:L/I:L/A:N). The CWE-94 classification typically relates to code injection, but here it is referenced in the context of HTML injection, which can be leveraged for malicious script execution or data manipulation. No patches or fixes are currently linked, and no known exploits have been reported in the wild, suggesting the vulnerability is newly disclosed or not yet weaponized. The vulnerability's exploitation could allow attackers to inject malicious HTML content that may lead to phishing, session hijacking, or defacement of the booking system interface, potentially undermining user trust and data integrity.

For European organizations, especially those in the hospitality and restaurant sectors using PHPJabbers Restaurant Booking System v3.0, this vulnerability poses a risk of unauthorized HTML injection leading to potential phishing attacks, data manipulation, or user interface tampering. Although the impact on availability is none, the confidentiality and integrity of user data could be compromised, potentially exposing customer information or allowing attackers to mislead users into divulging sensitive information. This could result in reputational damage, regulatory non-compliance (e.g., GDPR violations if personal data is exposed or manipulated), and financial losses. The ease of exploitation without authentication and user interaction increases the risk profile. Organizations relying on this software for online booking and customer interaction may face targeted attacks aiming to exploit this vulnerability to gain footholds or conduct social engineering campaigns. The lack of known exploits in the wild currently limits immediate risk, but proactive mitigation is essential to prevent future exploitation.

1. Monitor PHPJabbers official channels for patches or updates addressing CVE-2023-51317 and apply them promptly once available. 2. Implement strict input validation and sanitization on all user-supplied data, especially for the affected parameters ('name', 'plugin_sms_api_key', 'plugin_sms_country_code', 'title'), ensuring that HTML special characters are properly encoded or stripped. 3. Deploy a Web Application Firewall (WAF) with custom rules to detect and block suspicious input patterns indicative of HTML injection attempts targeting the booking system. 4. Conduct regular security assessments and code reviews of the booking system to identify and remediate injection vulnerabilities. 5. Educate staff and users about phishing risks that could arise from manipulated booking interfaces. 6. Consider isolating the booking system environment and restricting access to minimize potential lateral movement if exploited. 7. Maintain comprehensive logging and monitoring to detect anomalous activities related to injection attempts or unauthorized content changes.