PhpWeasyPrint vulnerable to PHAR deserialization via output filename (CVE-2023-28115 case-insensitive bypass)

PhpWeasyPrint is a PHP library allowing PDF generation from a URL or an HTML page. Prior to version 2.6.0, pontedilana/php-weasyprint guarded the output filename against the phar:// stream wrapper with a case-sensitive blacklist. PHP stream wrappers are case-insensitive, so PHAR://, Phar://, etc. bypass the check and reach fileExists() (file_exists()) in prepareOutput(). On PHP 7 (which the library still supports — PHP 7.4+), this triggers deserialization of a crafted PHAR archive's metadata, leading to remote code execution. This is the patch-bypass of CVE-2023-28115. The same issue and fix were handled upstream in KnpLabs/snappy (GHSA-92rv-4j2h-8mjj). PhpWeasyPrint version 2.6.0 contains a patch for the issue.