Magento installing Magento SUPEE 11155 along with the Magento 1.9.4.2 version to secure your Magento stores from cross-site scripting, arbitrary code execution, and sensitive data disclosure vulnerabilities as well as other security issues.
Methods to Install Magento SUPEE 11155:
Learn how to implement these methods at https://meetanshi.com/blog/install-magento-supee-11155/