Security Alert Summary
The WebStack theme for WordPress contains a vulnerability that allows unauthenticated arbitrary file uploads due to missing file type validation in a theme upload function. An attacker able to upload arbitrary files to the site server could potentially use that capability to run malicious code or otherwise compromise site data or availability.
CVE Details
- CVE ID: CVE-2026-1555
- Affected component: WebStack theme for WordPress
- Affected versions: All versions up to, and including, 1.2024
- Published: April 15, 2026 at 4:17:33 AM UTC
- Last modified: April 15, 2026 at 4:17:33 AM UTC
- CVSS v3.1: Base score 9.8, Severity: CRITICAL, Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Authentication / Privileges / User Interaction: Authentication: None (unauthenticated attacker); Privileges Required: None; User Interaction: None
- Primary impact: Confidentiality: High; Integrity: High; Availability: High
- Weakness (CWE): CWE-434 (Unrestricted Upload of File with Dangerous Type)
Technical Details
According to the available information, the vulnerability is caused by missing file type validation in the theme’s image upload function, identified as io_img_upload(). Because the function does not properly restrict or validate uploaded file types, an unauthenticated attacker can upload arbitrary files to the affected site server.
Arbitrary file uploads can allow an attacker to place executable code or other malicious content on the server. The advisory notes that this may make remote code execution possible; the extent of impact depends on server configuration, file locations writable by the upload routine, and any additional application-level checks or protections in place.
How This Could Impact Your Website
In a typical WordPress site with multiple users, an unauthenticated attacker exploiting this vulnerability could upload files that expose or modify site content or data. For example, an attacker might place scripts or web shells in an uploadable location, increasing the risk of data theft, content tampering, or service disruption. These activities could reveal internal user email addresses or other sensitive information, raising the risk of targeted phishing or social engineering against site staff, contractors, or contributors.
A realistic scenario: a site owner manages content with several internal editors and contractors who have contributor or author access. If the theme’s upload function is reachable without authentication, an attacker could upload malicious files, which might be used to harvest user data or alter pages. This could lead to increased phishing attempts against the organization and potential disruption to site availability or content integrity.
If youre unsure whether your site is affected or how to assess your current user roles and plugins, it may be worth having a professional review of your setup.
Recommended Actions
- Update the affected plugin or theme as soon as a patched version is available.
- Review and reduce unnecessary user roles and permissions, especially contributor and author accounts.
- Enforce strong passwords and enable two-factor authentication for editors and administrators.
- Remove unused or unmaintained plugins and themes to reduce attack surface.
- Monitor site activity and server logs for unusual file uploads, new files in upload directories, or unexpected PHP or script files.
If youd like help reviewing your plugins, user roles, or overall WordPress security posture, our team at Freshy is happy to help.
