Affected: Homebrew: charm-tools

### Impact

`FishActivator` defines no `quote()`, so it inherits `ViaTemplateActivator.quote`, which returns `shlex.quote(string)`. That function follows POSIX `sh` rules, where a backslash inside single quotes stays a literal character. fish reads `\'` inside single quotes as an escaped quote and `\\` as an escaped backslash. A value with a backslash before a quote therefore ends the literal somewhere other than where `shlex.quote` put the end, and fish expands the command substitution that follows.

The environment path reaches `set -gx VIRTUAL_ENV`, and `--prompt` or `VIRTUALENV_PROMPT` reaches `set -gx VIRTUAL_ENV_PROMPT`. For `--prompt "x\'\$(touch PWNED)'\'"`, the generated `activate.fish` contains:

```fish set -gx VIRTUAL_ENV_PROMPT 'x\'"'"'$(touch PWNED)'"'"'\'"'"'' ```

`source bin/activate.fish` runs `touch PWNED`, and fish prints no error. The same payload as a directory name runs through `VIRTUAL_ENV`. `--prompt .` takes the current directory's name, so running virtualenv inside a directory someone else named is enough. Without the backslash the payload runs nothing, and under bash it runs nothing either.

virtualenv generates `activate.fish` by default. An attacker needs to influence the environment path or prompt: a CI job or wrapper tool that passes a branch, project or job name through, or a directory in a cloned repository or unpacked archive.

The bug affects every release up to 21.14.1 that ships `activate.fish`. The GHSA-p58f-9548-mpm2 fix in 21.7.13 mov…

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.2, FishActivator inherits ViaTemplateActivator.quote(), which uses POSIX shlex.quote() even though fish interprets backslashes and single quotes differently. An attacker-influenced environment path, --prompt, or VIRTUALENV_PROMPT value containing a backslash before a quote can therefore terminate the generated fish literal and execute command substitution when the user sources activate.fish. This issue is fixed in version 21.14.2.

Affected: PyPI: virtualenv

### Impact

`FishActivator` defines no `quote()`, so it inherits `ViaTemplateActivator.quote`, which returns `shlex.quote(string)`. That function follows POSIX `sh` rules, where a backslash inside single quotes stays a literal character. fish reads `\'` inside single quotes as an escaped quote and `\\` as an escaped backslash. A value with a backslash before a quote therefore ends the literal somewhere other than where `shlex.quote` put the end, and fish expands the command substitution that follows.

The environment path reaches `set -gx VIRTUAL_ENV`, and `--prompt` or `VIRTUALENV_PROMPT` reaches `set -gx VIRTUAL_ENV_PROMPT`. For `--prompt "x\'\$(touch PWNED)'\'"`, the generated `activate.fish` contains:

```fish set -gx VIRTUAL_ENV_PROMPT 'x\'"'"'$(touch PWNED)'"'"'\'"'"'' ```

`source bin/activate.fish` runs `touch PWNED`, and fish prints no error. The same payload as a directory name runs through `VIRTUAL_ENV`. `--prompt .` takes the current directory's name, so running virtualenv inside a directory someone else named is enough. Without the backslash the payload runs nothing, and under bash it runs nothing either.

virtualenv generates `activate.fish` by default. An attacker needs to influence the environment path or prompt: a CI job or wrapper tool that passes a branch, project or job name through, or a directory in a cloned repository or unpacked archive.

The bug affects every release up to 21.14.1 that ships `activate.fish`. The GHSA-p58f-9548-mpm2 fix in 21.7.13 mov…