CVE-2026-61944 in Bookly Plugin
Summary
by MITRE • 07/23/2026
Unauthenticated Cross Site Scripting (XSS) in Bookly <= 27.7 versions.
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Analysis
by VulDB Data Team • 07/23/2026
This vulnerability represents a critical unauthenticated cross site scripting flaw affecting Bookly plugin versions up to and including 27.7. The issue stems from insufficient input validation and output encoding mechanisms within the plugin's handling of user-supplied data, particularly in parameters that are directly reflected in HTML responses without proper sanitization. The vulnerability is categorized under CWE-79 as a classic cross site scripting weakness where malicious scripts can be injected into web pages viewed by other users. Attackers can exploit this flaw by crafting malicious payloads that leverage the plugin's lack of proper input filtering, allowing them to execute arbitrary JavaScript code in the context of affected user sessions. The impact extends beyond simple data theft as it enables session hijacking, credential harvesting, and potential privilege escalation within the compromised environment. This vulnerability is particularly dangerous because it requires no authentication to exploit, making it accessible to any attacker who can influence input parameters passed to the vulnerable Bookly endpoints.
The technical exploitation occurs through manipulation of URL parameters or form fields that are processed by the plugin without adequate security controls. When user input containing malicious script tags is accepted and subsequently displayed in web responses without proper HTML encoding or sanitization, attackers can inject persistent or reflected XSS payloads that execute in victims' browsers. The vulnerability is consistent with ATT&CK technique T1566.001 which involves the exploitation of web application vulnerabilities for initial access. The flaw typically manifests when parameters such as booking IDs, user names, or custom form fields are improperly handled by the plugin's backend processing logic, creating opportunities for attackers to inject malicious code that persists in the application's response. This creates a persistent threat vector where compromised users' browsers become conduits for further attacks against other users within the same system.
The operational impact of this vulnerability is severe as it can lead to unauthorized access to sensitive booking data, user credentials, and personal information stored within the Bookly system. Once exploited, attackers can establish persistent backdoors through the injected scripts, potentially compromising entire user sessions and enabling long-term surveillance of booking activities. The vulnerability also affects the integrity of the application by allowing modification of displayed content, which can result in phishing attacks targeting other users or redirection to malicious sites. Organizations using affected Bookly versions face potential regulatory compliance issues as this vulnerability could result in unauthorized data access violating privacy regulations such as gdpr and ccpa. The impact extends beyond immediate security concerns to include business continuity risks, as compromised booking systems can disrupt operations and damage customer trust.
Mitigation strategies should focus on immediate patching of the affected Bookly plugin to version 27.8 or later where the XSS vulnerability has been addressed through proper input validation and output encoding mechanisms. Organizations must implement comprehensive input sanitization routines that filter and encode all user-supplied data before processing or display, following secure coding practices aligned with OWASP Top Ten recommendations. Network-based protections such as web application firewalls should be deployed to detect and block suspicious script injection attempts, while regular security audits of third-party plugins should be conducted to identify similar vulnerabilities. Additionally, implementing content security policies and disabling unnecessary user input fields can reduce the attack surface. Security monitoring should include detection of anomalous script patterns in web traffic, and regular penetration testing should verify that all input vectors have been properly secured. Organizations should also establish incident response procedures specifically designed to handle XSS exploitation attempts and maintain up-to-date vulnerability management processes to prevent similar issues in other plugins or applications.