Who can help with the analysis and audit of a WordPress site for vulnerabilities?

Question

Information Security

Hello.
There is a site that our company ordered from a third-party developer. Made on WordPress. The developer claims that not one of the standard templates is used, but completely written for us. There are doubts about this.
There are also doubts about vulnerabilities and holes on the site. Who could help in this matter? Or, advise someone who can help?
And in general, the site needs to be tested on all pages to look like and look for errors.