Code injection

Insecure temporary directory usage in frontend build functionality of com.vaadin:flow-server versions 2.0.9 through 2.5.2 (Vaadin 14.0.3 through Vaadin 14.5.2), 3.0 prior to 6.0 (Vaadin 15 prior to 19), and 6.0.0 through 6.0.5 (Vaadin 19.0.0 through 19.0.4) allows local users to inject malicious code into frontend resources during application rebuilds.