CVE-2026-1098 identifies a stored Cross-Site Scripting (XSS) vulnerability in the CM CSS Columns plugin for WordPress, specifically related to the 'tag' shortcode attribute. This vulnerability stems from insufficient input sanitization and output escaping of user-supplied attributes, allowing malicious scripts to be stored in the website content. Authenticated attackers with Contributor-level access or higher can exploit this by injecting arbitrary JavaScript code into pages via the vulnerable shortcode attribute. When other users access these pages, the injected scripts execute in their browsers, potentially compromising session tokens, redirecting users, or performing unauthorized actions. The vulnerability affects all plugin versions up to and including 1.2.1. The CVSS 3.1 score of 6.4 reflects a medium severity, with an attack vector over the network, low attack complexity, requiring privileges but no user interaction, and impacting confidentiality and integrity with a scope change. No patches or known exploits are currently documented, but the vulnerability is publicly disclosed and should be considered a risk for WordPress sites using this plugin. The CWE-79 classification confirms the nature as improper neutralization of input during web page generation, a common and impactful web vulnerability.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of their web applications. Exploitation could lead to session hijacking, unauthorized actions performed on behalf of users, data theft, or defacement of websites. This can damage organizational reputation, lead to data breaches involving personal or sensitive information, and potentially violate GDPR requirements for data protection. Since the vulnerability requires only Contributor-level access, insider threats or compromised accounts with limited privileges can be leveraged to escalate attacks. The scope change in the CVSS vector indicates that the vulnerability can affect resources beyond the initially compromised component, increasing the potential impact. Organizations relying on WordPress for public-facing or internal sites using the CM CSS Columns plugin are at risk of targeted attacks or automated exploitation once a public exploit emerges.

Immediate mitigation should focus on restricting Contributor-level user permissions and auditing existing user roles to minimize the number of users who can inject content. Administrators should monitor for unusual shortcode usage or unexpected script tags in page content. Since no official patch is currently available, organizations can implement manual input validation and output encoding for the 'tag' shortcode attribute by customizing the plugin or using WordPress hooks to sanitize inputs. Employing Web Application Firewalls (WAFs) with rules to detect and block malicious script injections targeting this plugin can provide additional protection. Regular backups and integrity checks of website content will help detect and recover from any successful exploitation. Once a patch is released, prompt updating of the plugin is critical. Additionally, educating content contributors about safe content practices and monitoring logs for suspicious activity will reduce exploitation risk.