# Command Injection¶ ↑

Some Ruby core methods accept string data that includes text to be executed as a system command.

They should not be called with unknown or unsanitized commands.

These methods include:

- `Kernel.exec`

- `Kernel.spawn`

- `Kernel.system`

- `command` (backtick method) (also called by the expression `%x[command]`).

- `IO.popen` (when called with other than `"-"`).

Some methods execute a system command only if the given path name starts with a `|`:

- `Kernel.open(command)`.

- `IO.read(command)`.

- `IO.write(command)`.

- `IO.binread(command)`.

- `IO.binwrite(command)`.

- `IO.readlines(command)`.

- `IO.foreach(command)`.

- `URI.open(command)`.

Note that some of these methods do not execute commands when called from subclass `File`:

- `File.read(path)`.

- `File.write(path)`.

- `File.binread(path)`.

- `File.binwrite(path)`.

- `File.readlines(path)`.

- `File.foreach(path)`.