Some of the web security threats are:
Malware: Malicious software or malware is software that is designed to cause harm to your website. It can allow a hacker to access your website's sensitive information or spam the users. Denial Of Service Attacks: A denial of service attack makes a website inaccessible to its users. A DoS attack slows down a website or crashes it completely by sending huge traffic to a website or triggering a crash.
Blacklisting: Blacklisting a website can result in it being removed from the result of a search engine. Often the website is flagged with warnings to keep visitors away.
Defacement: Defacement is the replacement of your website content with some malicious content. A cybercriminal can use your website to share malicious content, which can damage your website's reputation.
Exploiting Vulnerabilities: Websites that are not up to the mark with security can have a lot of vulnerabilities. A cybercriminal can access those vulnerabilities and access the sensitive data on your website.