CVE-2025-4839 is a vulnerability identified in the itwanger paicoding software versions 1.0.0 through 1.0.3. The issue resides in the CrossUtil.java file within the paicoding-core module, specifically related to the implementation of cross-domain policies. The vulnerability manifests as a permissive cross-domain policy that includes untrusted domains, potentially allowing malicious domains to bypass same-origin restrictions. This can lead to unauthorized access or interaction with resources that should be restricted, potentially enabling cross-site scripting (XSS), data theft, or other cross-origin attacks. The vulnerability can be exploited remotely without requiring authentication; however, the attack complexity is rated as high, and exploitation is considered difficult. The CVSS v4.0 base score is 2.3, indicating a low severity, primarily due to the high attack complexity and the requirement for user interaction. The vulnerability does not affect confidentiality or availability significantly but has a low impact on integrity. No known exploits are currently active in the wild, and no patches have been published yet. The public disclosure of the exploit details increases the risk of future exploitation attempts.

For European organizations using the affected versions of paicoding, the permissive cross-domain policy could expose web applications to cross-origin attacks, potentially leading to unauthorized data access or manipulation. While the direct impact is low severity, organizations handling sensitive user data or critical business functions could face reputational damage or compliance issues if exploited. The requirement for user interaction and high attack complexity reduces the likelihood of widespread exploitation, but targeted attacks against high-value assets remain a concern. Additionally, organizations in sectors with strict data protection regulations (e.g., GDPR) must consider the risk of data leakage or unauthorized access resulting from this vulnerability.

Organizations should immediately assess their use of paicoding versions 1.0.0 to 1.0.3 and plan for an upgrade once a patched version is released. In the interim, review and tighten cross-domain policies to restrict allowed domains explicitly, removing any untrusted or unnecessary domains. Implement Content Security Policy (CSP) headers to limit the sources of executable scripts and reduce the risk of cross-origin attacks. Conduct thorough code reviews of cross-domain policy implementations and consider deploying web application firewalls (WAFs) with rules targeting suspicious cross-origin requests. Educate users about the risks of interacting with untrusted links or domains to mitigate the user interaction requirement. Monitor network traffic for unusual cross-origin requests that could indicate exploitation attempts.