Security risk?

Not necessarily. Usually the main poster on a blog is also the admin so if your posts show who wrote the post then it is also showing the admin.

If it is really a concern you could create a 2nd user who is the author of your posts and have a different ID who has the admin role

Most hackers trying to force your site if you use the old default of “admin” so you should really change it.

Check this out:

https://www.ads-software.com/support/topic/how-to-change-admin-username?replies=4