Header injection in HTTP responses can allow for HTTP response splitting, session fixation via the Set-Cookie header, cross-site scripting (XSS), and malicious redirect attacks via the location header.
Header injection in HTTP responses represents a significant security concern as it allows attackers to manipulate and exploit data within response headers, leading to potential vulnerabilities such as splitting response headers, exploiting session fixation via the Set-Cookie header, executing XSS attacks, and triggering malicious redirects using the location header.