Salon Booking System < 10.31.11 - Salon Staff+ Stored XSS and SSRF via Salon REST 'image_url'

The Salon Booking System WordPress plugin before 10.31.11 does not validate a user-supplied image URL before fetching it server-side and writing the response to a publicly accessible location under an attacker-chosen filename, allowing users with the Salon Staff role or higher to force the server to read internal-only resources and disclose them, and to store a malicious SVG that runs arbitrary scripts in the site's origin for anyone who opens it.