As with all types of software, online security extensions are not inherently safe or unsafe. It depends on a variety of factors, including who developed them, how they're maintained, and what permissions they require. There are many legitimate and effective security extensions for web browsers developed by reputable companies with a strong track record of protecting user privacy and security. These extensions can significantly boost your online security by blocking malicious websites, protecting against tracking, and securing your data. However, there are also malicious or poorly designed extensions that can actually harm your security and privacy. They might contain malware, spyware, or vulnerabilities that hackers can exploit.