Fix for Magento 2.1 WYSIWYG embedding media with incorrect URLs - not transforming them into media tags. Related issue: magento/magento2#6138
composer config repositories.talv/magento2-wysiwyg-fix vcs https://github.com/talv/magento2-wysiwyg-fix/
composer require talv/magento2-wysiwyg-fix
bin/magento module:enable Talv_WysiwygFix
bin/magento setup:upgrade --keep-generated