CVE-2026-34559 is a stored cross-site scripting (XSS) vulnerability in the ci4ms product of the ci4-cms-erp project. Before version 0.31.0.0, the application does not properly neutralize user-controlled input when creating or editing blog tags, specifically the tag name field. Malicious JavaScript code injected into this field is stored on the server and later rendered unsafely in both public and administrative interfaces, leading to stored XSS. The vulnerability has a CVSS 3.1 score of 9.1, indicating critical severity. The issue was patched in version 0.31.0.0.

Successful exploitation allows an attacker with at least low privileges to inject persistent malicious scripts that execute in the context of users viewing affected tag pages or administrative interfaces. This can lead to high confidentiality impact by stealing sensitive information, limited integrity impact, and limited availability impact. The vulnerability affects all versions prior to 0.31.0.0.

Upgrade to ci4ms version 0.31.0.0 or later, where the vulnerability has been patched. No other mitigations are specified or required once the official fix is applied.