In an ongoing blackhat SEO campaign, scammers are using open redirects found on government websites to redirect visitors to pornography sites. An open redirect is an URL that anyone can use to redirect a visitor to a website of their choosing. The National Weather Service, Louisiana State Senate, Dwight D. Eisenhower Memorial, Colorado Department of Higher Education, and many more federal and local government sites were abused in this SEO campaign. It is not known at this time how the SEO. attackers are conducted by hacking into WordPress sites and then creating pages containing hundreds of URLs that they want to be indexed.
Source: https://www.bleepingcomputer.com/news/security/us-government-sites-abused-to-redirect-users-to-porn-sites/