Textpattern CMS 4.9.0 contains a broken access control flaw that enables authenticated users with low privileges to alter articles belonging to users with higher privileges. The vulnerability arises when the article ID parameter is manipulated during the duplicate-and-save workflow in txp_article.php, allowing an attacker to bypass authorization checks and overwrite target content. This flaw can be leveraged to tamper with confidential or strategically important articles, impacting the integrity of published material and potentially leading to misinformation or loss of trust.

The vulnerability affects Textpattern CMS version 4.9.0 and potentially earlier releases that have not applied the patch included in the 4.9.1 security release. It specifically targets the article management subsystem located in txp_article.php and the duplicate-and-save operation exposed to authenticated users.

EPSS score is less than 1% and the vulnerability is not listed in CISA KEV. With a CVSS score of 6.5, the flaw enables privilege escalation within the CMS, allowing authenticated users to overwrite content owned by higher-privilege users. The attack vector is an authenticated user manipulating the article ID parameter during the duplicate-and-save workflow. The medium severity combined with the ability to compromise content integrity indicates a significant risk that warrants prompt mitigation.