RabbitMQ is a messaging and streaming broker. Versions prior to 4.0.3 are vulnerable to a sophisticated attack that could modify virtual host name on disk and then make it unrecoverable (with other on disk file modifications) can lead to arbitrary JavaScript code execution in the browsers of management UI users. When a virtual host on a RabbitMQ node fails to start, recent versions will display an error message (a notification) in the management UI. The error message includes virtual host name, which was not escaped prior to open source RabbitMQ 4.0.3 and Tanzu RabbitMQ 4.0.3, 3.13.8. An attack that both makes a virtual host fail to start and creates a new virtual host name with an XSS code snippet or changes the name of an existing virtual host on disk could trigger arbitrary JavaScript code execution in the management UI (the user's browser). Open source RabbitMQ "4.0.3" and Tanzu RabbitMQ "4.0.3" and "3.13.8" patch the issue.