OpenCTI 3.3.1 is vulnerable to a directory traversal attack via the static/css endpoint. An unauthenticated attacker can read arbitrary files from the filesystem by sending crafted GET requests with path traversal sequences (e.g., '../') in the URL. For example, requesting /static/css//../../../../../../../../etc/passwd returns the contents of /etc/passwd. This vulnerability was discovered by Raif Berkay Dincel and confirmed on Linux Mint and Windows 10.