CVE-2022-42747 is a reflected Cross-Site Scripting (XSS) vulnerability identified in CandidATS version 3.0.0, specifically affecting the 'sortBy' parameter of the 'ajax.php' resource. This vulnerability arises because the application fails to properly validate or sanitize user-supplied input, allowing an attacker to inject malicious scripts that are reflected back to the victim's browser. When a user interacts with a crafted URL containing malicious code in the 'sortBy' parameter, the injected script executes in the context of the victim's browser session. This can lead to the theft of cookies, which may contain session tokens or other sensitive information, enabling attackers to hijack user sessions or impersonate users. The vulnerability is categorized under CWE-79, which pertains to improper neutralization of input during web page generation. The CVSS v3.1 base score is 6.1 (medium severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), user interaction required (UI:R), scope changed (S:C), and low impact on confidentiality and integrity (C:L/I:L) but no impact on availability (A:N). There are no known exploits in the wild, and no patches have been linked yet. The vulnerability was published on November 3, 2022.

For European organizations using CandidATS version 3.0.0, this vulnerability poses a risk primarily to the confidentiality and integrity of user sessions. Successful exploitation could allow attackers to steal session cookies, leading to unauthorized access to user accounts and potentially sensitive data. This can result in data breaches, loss of user trust, and compliance violations under regulations such as GDPR. Since the vulnerability requires user interaction (e.g., clicking a malicious link), phishing campaigns could be a likely attack vector. The scope change in the CVSS vector indicates that exploitation can affect resources beyond the vulnerable component, potentially impacting other parts of the application or user data. Although availability is not impacted, the compromise of user sessions can disrupt business operations and lead to reputational damage. The medium severity suggests that while the threat is significant, it is not critical, but organizations should prioritize remediation to prevent exploitation.

1. Immediate mitigation should involve implementing proper input validation and output encoding on the 'sortBy' parameter in the 'ajax.php' resource to neutralize any injected scripts. Use established libraries or frameworks that provide XSS protection. 2. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in the browser context. 3. Educate users and staff about phishing risks and the dangers of clicking on suspicious links, as user interaction is required for exploitation. 4. Monitor web application logs for unusual or suspicious requests targeting the 'sortBy' parameter to detect potential exploitation attempts. 5. If possible, upgrade to a patched version of CandidATS once available or apply vendor-provided patches promptly. 6. Implement secure cookie attributes such as HttpOnly and Secure flags to reduce the risk of cookie theft via XSS. 7. Conduct regular security assessments and penetration testing focusing on input validation and XSS vulnerabilities in web applications.