Should I care?

Absolutely!

By inserting contents in your site, attackers may take control of it: execute code, access sensitive data, destroy information, steal your intellectual property...

They can attack your users and send them payloads that infect their computers with malware.

And the modifications of your pages will be indexed by search engines. Your site can appear when people look for drugs, ilegal products or porn. Its reputation, the reputation of your organization, may ve severely affected.

Even if you think you have no important information or services on your web, you may be a target when all they want is to have links pointing to their sites.

Next: How do I detect them?