PhpSpreadsheet is a PHP library for reading and writing spreadsheet files. Versions prior to 3.7.0, 2.3.5, 2.1.6, and 1.29.7 are vulnerable to bypass of the cross-site scripting sanitizer using the javascript protocol and special characters. An attacker can use special characters, so that the library processes the javascript protocol with special characters and generates an HTML link. Versions 3.7.0, 2.3.5, 2.1.6, and 1.29.7 contain a patch for the issue.