### Impact
The generated `activate` (bash/zsh) and `activate.fish` scripts interpolate a `shlex.quote`-ed value into a position that quotes it a second time. The extra quotes terminate the quoted run early and leave part of the value parsed as shell code, so a path containing shell metacharacters runs commands when a user sources the activation script.
`activate` is affected through the virtual environment's own path, on the branch that reports a relocated environment:
```sh
echo "Virtual environment directory __VIRTUAL_ENV__ does not exist!" >&2
```
For a destination named `x'$(id)'y`, `shlex.quote` emits `'x'"'"'$(id)'"'"'y'`. The inner `"` closes the enclosing double quote and `$(id)` is left unquoted. Backtick and `;` payloads reach the same result. This branch runs whenever the recorded path is absent, which is the normal case for a virtual environment copied or distributed to another machine.
`activate.fish` is affected through the interpreter's Tcl/Tk library paths:
```fish
set -gx TCL_LIBRARY '__TCL_LIBRARY__'
```
`shlex.quote` already returns `'/tcl/(cmd)/lib'`, so the rendered line is `''/tcl/(cmd)/lib''`. fish concatenates the adjacent quoted runs and expands the `(cmd)` left between them. The same doubling also splits a path containing a space into two list elements, corrupting `TCL_LIBRARY` and `TK_LIBRARY`.
This is the same defect class as GHSA-x78j-v8h9-3j2q, which covered `activate.bat`.
### Patches
Fixed in 21.7.13 by moving the placeholders outside the surrounding quotes, so each value keeps only the quoting `shlex.quote` applied. Fix: https://github.com/pypa/virtualenv/pull/3252
### Workarounds
Avoid creating or distributing virtual environments whose path contains `'`, `` ` ``, `$`, `;`, `(` or `)`, and inspect the generated activation script before sourcing one you did not create.