The latest Mendix version has the newest security patches and the newest bugfixes. Therefore it is recommended to always keep up to date with Mendix releases.
This does not include releases that have breaking changes. For example, upgrading from 6 to 7 is not required.
Using a Mendix release that is not officially supported such as version 5 is also a violation of this rule.
To fix the violation update to the latest minor version for your major Mendix version within one month of its release. For example, if the project is on Mendix version 6 it needs to be on the latest minor version which at the moment of writing is 6.10.19 within one month of its release.