The job of the product backlog is to represent all the ideas that anyone in the application food chain has had about the product, the customer, and the sales team. The fact that these ideas are in the backlog means they aren’t priority tasks, but are still important enough that they are captured. Moving something into the backlog in this way, and identifying it as a future task, is a business decision.
However, you cannot use the backlog for non-functional requirements, especially the ones that have security implications. You have to have a separate project to hold and track those tickets, such as a Jira or a GitHub project.
Security issues or refactoring needs, still exist, regardless of whether the product owner wants to pursue them, whether they are a priority, or whether customers are asking for them.
Security and quality issues should either be in a fixed state, or in a risk acceptance state.
The difference is that quality and security tickets represents reality, whereas the backlog represents the ideas that could be developed in the future. That is why they have very different properties, and why you shouldn’t have quality and security tickets in the backlog Pit of Despair