In order to allow users of MySQL 5.5 more time to upgrade their database engines, we have recently changed our MySQL 5.5 roadmap to remove several cPanel & WHM upgrade blockers.
If you run MySQL 5.5 on cPanel & WHM version 78, you can upgrade to 86. You cannot upgrade to 88 or 90. If you run 5.5 on cPanel & WHM version 86, you can upgrade to 92.
Even though a cPanel & WHM version may allow you to run MySQL 5.5, that version of MySQL it still end-of-lifed; cPanel, L.L.C. will thus be unable provide support for any technical issues that you have with the database.
We strongly encourage you to upgrade MySQL to a supported version as soon as possible in order to avoid any vulnerabilities or incompatibilities with third-party applications such as WordPress®.
If you run MySQL 5.5, we’d like to hear from you as to why you are still running this out-of-date software and what is preventing you from upgrading to a supported version. Please take our survey about MySQL 5.5 support: https://go.cpanel.net/mysql55forums