The DomainTools Whois plugin will automatically link domain names in a WordPress page or blog post to the DomainTools Whois service. It also generates a pop-up containing a summary of Whois information that your visitors can see without leaving your site.

DomainTools Whois Plugin

DomainTools whois plugin shows whois data for domains found in blog articles and links them to whois.domaintools.com.

Mahamodul Hasan Khan

dnsLT is a little tools for Searching Domain whois & showing in any kind 
of WordPress Site. You don’t need to do a simple code for that. Just put 
the ShortCode in your page or post or anywhere it will show a search 
form for domain whois. Then your visitor will able to search any domain 
whois from there. You can config colors with your site color from admin 
settings in free version. also can do many things from pro version.

dnsLT Free domain name whois

A plugin for search domain whois from your lovely web site.

DomainTools Whois Plugin vs dnsLT Free domain name whois