CVE-2026-48943: K2 ≤2.24 Mass-Assignment in User Profile Plugin

Technical summary

CVE-2026-48943 is a mass-assignment vulnerability in the K2 user plugin (plg_user_k2) affecting K2 version 2.24 and earlier. The vulnerability exists in the handling of the com_users profile.save request handler. When a POST request includes the parameter K2UserForm=1, the plugin fails to properly validate and restrict which database columns can be written to, allowing an authenticated user to directly set values in the notes, image, and plugins columns of the #__k2_users database table. These fields are not editable through the K2 frontend interface, meaning the vulnerability bypasses intended access controls.

Business impact

This vulnerability enables registered users to alter their own K2 user records in ways administrators cannot audit or control through the normal interface. Potential impacts include: defacing user profiles by injecting unauthorized notes or images, manipulating plugin associations to gain unintended functionality, and creating audit trail inconsistencies. While the flaw requires existing Joomla registration, sites with open user registration or those with many active users face higher risk. The ability to modify hidden fields could also enable privilege escalation attempts if those fields are later used in access control logic.

Affected systems

JoomlaWorks K2 version 2.24 and all earlier versions running on Joomla installations. The vulnerability is limited to sites that: (1) have K2 installed and enabled, (2) allow registered user accounts, and (3) permit users to edit their own profiles. Default Joomla installations with K2 are affected.

Exploitability

Exploitability is straightforward. An attacker needs only a valid Joomla user account (which is often freely obtainable if the site permits registration) and the ability to make an HTTP POST request. No special tools, authentication bypass, or social engineering are required. The attack is repeatable and leaves clear traces in the database. The CVSS 3.1 score of 6.5 (Medium) reflects the requirement for prior authentication and the information disclosure and modification impact combined.

Remediation

Update K2 to a version after 2.24 that includes a fix for mass-assignment in the user plugin. Verify the patch release notes confirm that the K2UserForm parameter handling has been hardened to reject or whitelist only safe fields. As an interim measure, if updating is delayed, consider restricting which user roles can edit profiles or disabling user profile editing entirely if not needed.

Patch guidance

Check the JoomlaWorks website or your Joomla extension manager for K2 updates released after June 28, 2026 (the last known modification date for this CVE). Apply the patch to your K2 component through your Joomla administrator panel. Test the update in a staging environment first to ensure no profile edit workflows are broken. Verify that the K2UserForm parameter is no longer accepted in profile.save requests after patching.

Detection guidance

Monitor for POST requests to index.php?option=com_users&task=profile.save that include the K2UserForm=1 parameter. Check the #__k2_users table for suspicious modifications to the notes, image, or plugins columns that do not correspond to admin actions or legitimate user submissions. Review Joomla access logs for registered users sending profile update requests, especially repeated attempts. Examine the K2 user table for entries where the notes field contains unexpected content or the image field points to external or unusual paths.

Why prioritize this

Although rated CVSS 6.5 (Medium), this vulnerability should be prioritized if your Joomla site relies on K2 for content management and has active user communities. The ease of exploitation and lack of KEV status (not yet formally tracked) may mean slower discovery and patching in the wild. Mass-assignment flaws are a known attack pattern; early patching prevents account takeover chains or reputation damage from profile defacement.

Risk score, explained

CVSS 3.1 score of 6.5 reflects: (1) Network-accessible attack vector, (2) low attack complexity (no special conditions required beyond authentication), (3) requirement for prior authentication (reduces initial risk), and (4) combined impacts of low confidentiality and low integrity loss. The score does not escalate to 'High' because the vulnerability does not enable system compromise or denial of service, and it requires an existing user account. However, the low barrier to exploitation warrants urgent attention in live environments.

Frequently asked questions