Unescaped deployment environment variables in generated setup commands

Improper Neutralization of Special Elements used in an OS Command (OS Command Injection) vulnerability in livebook-dev livebook allows command injection into generated deployment setup commands. LivebookWeb.Hub.Teams.DeploymentGroupAgentComponent.docker_instructions/2 and LivebookWeb.Hub.Teams.DeploymentGroupAgentComponent.fly_instructions/4 in lib/livebook_web/live/hub/teams/deployment_group_agent_component.ex interpolate deployment group environment variable values into the generated Docker and Fly.io setup commands without shell escaping. The values originate from the deployment group configuration and reach the sinks through Livebook.Hubs.Dockerfile.online_docker_info/3. Both sinks place the value inside a double-quoted shell word, so a value containing a command substitution such as $(...) or backticks is evaluated by the shell without any need to break out of the quoting, and a literal double quote terminates the quoted word and allows arbitrary further tokens. The generated command is displayed in the Livebook web interface with a copy button, so a user who copies it and runs it without reviewing it first executes the injected commands on their own machine, under their own account. An attacker requires privileges sufficient to set deployment group environment variables, while the resulting code execution occurs on the machine of whoever runs the generated command. The Kubernetes instructions are not affected, because they render the same values into a YAML manifest with escaping rather than into a shell command. This issue affects livebook: from 0.13.0 before 0.18.7 and from 0.19.0 before 0.19.9.