CVE-2018-3763 : Security Advisory and Response

Nextcloud Calendar versions 1.5.8 and 1.6.1 had a vulnerability that allowed privileged users to execute a stored cross-site scripting (XSS) attack through the autocomplete search feature.

Understanding CVE-2018-3763

What is CVE-2018-3763?

CVE-2018-3763 is a vulnerability in Nextcloud Calendar versions 1.5.8 and 1.6.1 that could be exploited by privileged users to conduct a stored XSS attack.

The Impact of CVE-2018-3763

The vulnerability allowed administrators or group admins to store malicious scripts in autocomplete search results, potentially leading to XSS attacks that required user interaction. It specifically affected group names.

Technical Details of CVE-2018-3763

Vulnerability Description

In Nextcloud Calendar versions before 1.5.8 and 1.6.1, a lack of sanitization in autocomplete search results could enable a stored XSS attack, requiring user interaction. The issue was limited to group names.

Affected Systems and Versions

Product: Nextcloud Calendar application
Vendor: Nextcloud
Versions Affected: <1.6.1, <1.5.8

Exploitation Mechanism

The vulnerability could be exploited by privileged users, such as administrators or group admins, to insert malicious scripts into autocomplete search results, potentially leading to XSS attacks.

Mitigation and Prevention

Immediate Steps to Take

Upgrade Nextcloud Calendar to version 1.6.1 or higher to mitigate the vulnerability.
Regularly monitor and review autocomplete search results for any suspicious entries.

Long-Term Security Practices

Educate users on safe browsing practices to prevent XSS attacks.
Implement strict input validation and output encoding to prevent script injection.

Patching and Updates

Apply security patches and updates provided by Nextcloud to address known vulnerabilities.