A Cascading Style Sheets (CSS) injection vulnerability in Swagger UI before 3.23.11 allows attackers to use the Relative Path Overwrite (RPO) technique to perform CSS-based input field value exfiltration, such as exfiltration of a CSRF token value. In other words, this product intentionally allows the embedding of untrusted JSON data from remote servers, but it was not previously known that <style>@import within the JSON data was a functional attack method.
The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.