Contao 5.4.1 allows an authenticated admin account to upload a SVG file containing malicious javascript code into the target system. If the file is accessed through the website, it could lead to a Cross-Site Scripting (XSS) attack or execute arbitrary code via a crafted javascript to the target.
https://grimthereaperteam.medium.com/contao-5-4-1-malicious-file-upload-xss-in-svg-30edb8820ecb