OpenCTI 3.3.1 is vulnerable to a reflected cross-site scripting (XSS) attack via the /graphql endpoint. An attacker can inject arbitrary JavaScript code by sending a crafted GET request with a malicious payload in the query string, leading to execution of JavaScript in the victim's browser. For example, a request to /graphql?'"--></style></scRipt><scRipt>alert('Raif_Berkay')</scRipt> will trigger an alert. This vulnerability was discovered by Raif Berkay Dincel and confirmed on Linux Mint and Windows 10.