The vulnerability in Quarkus REST arises when REST endpoints are implemented without a CDI scope and utilize field injection for request parameters. In such cases, a single instance of the endpoint class is shared across multiple concurrent requests, leading to the potential exchange of request parameters between these requests. This means that data such as HTTP headers, URI templates, cookies, and form values from one request can inadvertently be accessed by another, posing significant security risks.Affected applications should ensure proper scoping with @RequestScoped or avoid field injection for request parameters. The issue is fixed in version 3.18.2.