GHSA-g47h-fgcw-g4ph: Algernon engine and themes vulnerable to Cross-site Scripting

All versions of the package github.com/xyproto/algernon/engine; all versions of the package github.com/xyproto/algernon/themes are vulnerable to Cross-site Scripting (XSS) via the themes.NoPage(filename, theme) function due to improper user input sanitization. Exploiting this vulnerability is possible when a file/resource is not found.