Dompdf: Embedded SVG images can leak existence of files and directories within the filesystem

Dompdf is an HTML to PDF converter for PHP. In versions 3.15 and prior, if a malicious actor can supply unrestricted content for rendering by Dompdf they can utilize the SVG rendering functionality to leak filesystem information when rendering PDF files using image references within a data-URI encoded SVG document. Using an <image> element inside a data-URI embedded SVG, an attacker can attempt to embed other files via the href or xlink:href attributes. When processing a file that does not exist (e.g. file:///DOESNOTEXIST), dompdf behaves differently than it does when accessing a file or directory that actually exists on the filesystem. This issue has been fixed in version 3.16.