CVE-2023-48314 is a high-severity cross-site scripting (XSS) vulnerability affecting Collabora Online, a collaborative online office suite built on LibreOffice technology. Specifically, the vulnerability exists in the Collabora Online Built-in CODE Server app (richdocumentscode) used in conjunction with Nextcloud. The flaw arises from improper neutralization of input during web page generation via the proxy.php component, allowing an attacker to inject malicious scripts. This vulnerability is classified under CWE-79, which pertains to improper input sanitization leading to XSS. Exploitation requires no privileges (PR:N), can be performed remotely over the network (AV:N), and only requires user interaction (UI:R), such as clicking a crafted link or opening a malicious document. The vulnerability impacts confidentiality, integrity, and availability (C:L/I:L/A:L) and has a CVSS v3.1 score of 7.1, indicating a high severity. The scope is changed (S:C), meaning the vulnerability can affect resources beyond the vulnerable component. The vulnerability was published on December 1, 2023, and fixed in Collabora Online Built-in CODE Server version 23.5.403. No known exploits are currently in the wild, and no workarounds exist, making timely patching critical. The vulnerability could allow attackers to execute arbitrary JavaScript in the context of the victim’s browser session, potentially leading to session hijacking, data theft, or further exploitation within the Nextcloud environment.

For European organizations, the impact of CVE-2023-48314 can be significant, especially for those relying on Nextcloud integrated with Collabora Online for document collaboration and productivity. Successful exploitation could lead to unauthorized access to sensitive documents, leakage of confidential information, and compromise of user sessions. This is particularly critical for sectors handling sensitive personal data or intellectual property, such as finance, healthcare, government, and legal services. The vulnerability’s ability to affect confidentiality, integrity, and availability means attackers could manipulate documents, disrupt collaboration workflows, or use the platform as a pivot point for broader network attacks. Given the widespread adoption of Nextcloud and Collabora Online in Europe as open-source alternatives to proprietary office suites, many organizations could be exposed if they have not applied the patch. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, as attackers may develop exploits rapidly once the vulnerability is public. The requirement for user interaction means phishing or social engineering could be used to trigger the attack, increasing the risk in environments with less mature security awareness.

1. Immediate upgrade of Collabora Online Built-in CODE Server to version 23.5.403 or later is essential to remediate the vulnerability. 2. Review and restrict access to the proxy.php endpoint to trusted users and networks where possible, using network segmentation and firewall rules. 3. Implement Content Security Policy (CSP) headers to reduce the impact of potential XSS attacks by restricting the execution of unauthorized scripts. 4. Enhance user awareness training focused on phishing and social engineering tactics to reduce the likelihood of users triggering the vulnerability. 5. Monitor Nextcloud and Collabora Online logs for unusual activity or access patterns that could indicate exploitation attempts. 6. Consider deploying web application firewalls (WAFs) with rules targeting XSS payloads to provide an additional layer of defense. 7. Regularly audit and update all integrated components and dependencies to ensure no residual vulnerabilities remain. 8. For organizations unable to immediately patch, isolate the affected services and limit user access until the update can be applied.