Shescape is a simple shell escape package for JavaScript. Affected versions were found to have insufficient escaping of white space when interpolating output. This issue only impacts users that use the `escape` or `escapeAll` functions with the `interpolation` option set to `true`. The result is that if an attacker is able to include whitespace in their input they can: 1. Invoke shell-specific behaviour through shell-specific special characters inserted directly after whitespace. 2. Invoke shell-specific behaviour through shell-specific special characters inserted or appearing after line terminating characters. 3. Invoke arbitrary commands by inserting a line feed character. 4. Invoke arbitrary commands by inserting a carriage return character. Behaviour number 1 has been patched in [v1.5.7] which you can upgrade to now. No further changes are required. Behaviour number 2, 3, and 4 have been patched in [v1.5.8] which you can upgrade to now. No further changes are required. The best workaround is to avoid having to use the `interpolation: true` option - in most cases using an alternative is possible, see [the recipes](https://github.com/ericcornelissen/shescape#recipes) for recommendations. Alternatively, users may strip all whitespace from user input. Note that this is error prone, for example: for PowerShell this requires stripping `'\u0085'` which is not included in JavaScript's definition of `\s` for Regular Expressions.

Affected: npm: shescape

### Impact

This only impacts users that use the `escape` or `escapeAll` functions with the `interpolation` option set to `true`. Example:

```javascript import cp from "node:child_process"; import * as shescape from "shescape";

// 1. Prerequisites const options = { shell: "bash", // Or shell: "dash", // Or shell: "powershell.exe", // Or shell: "zsh", // Or shell: undefined, // Only if the default shell is one of the affected shells. };

// 2. Attack (one of multiple) const payload = "foo #bar";

// 3. Usage let escapedPayload; shescape.escape(payload, { interpolation: true }); // Or shescape.escapeAll(payload, { interpolation: true });

cp.execSync(`echo Hello ${escapedPayload}!`, options); // _Output depends on the shell being used_ ```

The result is that if an attacker is able to include whitespace in their input they can:

1. Invoke shell-specific behaviour through shell-specific special characters inserted directly after whitespace. - Affected shells: _Bash_, _Dash_, _Zsh_, _PowerShell_ 2. Invoke shell-specific behaviour through shell-specific special characters inserted or appearing after line terminating characters. - Affected shells: _Bash_ 3. Invoke arbitrary commands by inserting a line feed character. - Affected Shells: _Bash_, _Dash_, _Zsh_, _PowerShell_ 3. Invoke arbitrary commands by inserting a carriage return character. - Affected Shells: _PowerShell_

### Patches

Behaviour number 1 has been patched in [v1.5.7] which you can…