Kentico Xperience before 13.0.178 has a specific set of allowed ContentUploader file extensions for unauthenticated uploads; however, because .zip is processed through TryZipProviderSafe, there is additional functionality to create files with other extensions. NOTE: this is a separate issue not necessarily related to SVG or XSS.
Kentico Xperience before 13.0.181 allows authenticated users to distribute malicious content (for stored XSS) via certain interactions with the media library file upload feature.