Kavita is a cross platform reading server. Opening an ebook with malicious scripts inside leads to code execution inside the browsing context. Kavita doesn't sanitize or sandbox the contents of epubs, allowing scripts inside ebooks to execute. This vulnerability was patched in version 0.8.1.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.