virtualenv: Generated files can follow existing destination links

Summary Generated activation files and pyvenv.cfg can follow existing links and write outside the requested environment. The template writer tests exists before unlinking, which misses dangling symlinks; the configuration writer opens the existing path directly. Anthropic's OSS Scanner reported...

USN-6012-1 smarty3 vulnerability

It was discovered that Smarty incorrectly parsed blocks' names and included files' names. A remote attacker with template writing permissions could use this issue to execute arbitrary PHP code. CVE-2022-29221...