PHPSpreadsheet is a pure PHP library for reading and writing spreadsheet files. One of the sample scripts in PhpSpreadsheet is susceptible to a cross-site scripting (XSS) vulnerability due to improper handling of input where a number is expected leading to formula injection. The code in in `45_Quadratic_equation_solver.php` concatenates the user supplied parameters directly into spreadsheet formulas. This allows an attacker to take control over the formula and output unsanitized data into the page, resulting in JavaScript execution. This issue has been addressed in release versions 1.29.2, 2.1.1, and 2.3.0. All users are advised to upgrade. There are no known workarounds for this vulnerability.