Yamcs 5.8.6 allows XSS (issue 2 of 2). It comes with a Bucket as its primary storage mechanism. Buckets allow for the upload of any file. There's a way to upload an HTML file containing arbitrary JavaScript and then navigate to it. Once the user opens the file, the browser will execute the arbitrary JavaScript.
https://www.linkedin.com/pulse/yamcs-vulnerability-assessment-visionspace-technologies
https://github.com/yamcs/yamcs/compare/yamcs-5.8.6...yamcs-5.8.7