OctoPrint provides a web interface for controlling consumer 3D printers. From 2.0.0rc1 until 2.0.0rc7, an authenticated user can supply a crafted default port or baudrate through a connect request to the bundled Serial Connector plugin. OctoPrint persists these values in printerConnection.preferred.parameters.port or printerConnection.preferred.parameters.baudrate and renders them as HTML when another user views the saved connection parameters, allowing script execution in that user's browser and actions within the user's OctoPrint access. This issue is fixed in version 2.0.0rc7.