Using XSS or cross server scripting, SEO poisoning attacks are primarily attacks on famous websites. IFrame viruses also act like this which are the most dangerous viruses and most common SEO poisoning attack that attack websites online through FTP password leakage or low server. Then these viruses target to different sites which contains some exploit matters, content and images.
Malicious hackers target this case when a very popular page with proper SEO. They do exploit the input and display vulnerablity on these websites.
SEO poisoning attack is also known as Blackhat SEO attack when hackers manipulate search engine results in order to make their links appear higher than legitimate results. As a user searches for related terms, the infected links appear near the top of the search results, producing a greater number of clicks to malicious Web sites.
SEO poisoning is one of the major methods of attack that you are seeing being used by online criminals at the moment.