PHPUnit is a testing framework for PHP. From 13.4.0 until 13.4.4, the TestCase::coverageFilesDirectory() logic in src/Runner/Phpt/TestCase.php creates temporary files for PHPT code coverage in a predictable phpunit-phpt directory under sys_get_temp_dir() and reuses that directory without verifying its ownership or permissions. On multi-user systems with a shared temporary path, a local attacker who creates the directory before the developer runs PHPT tests with code coverage can replace the generated job file before the child process executes it with require, allowing arbitrary code execution with the developer's privileges while the test and coverage report appear successful. PHPUnit 12.5 and earlier, default macOS and Windows configurations with per-user temporary directories, and single-user environments where another user cannot create files in the temporary path are not affected. This issue is fixed in 13.4.4.

Affected: Packagist: phpunit/phpunit

### Summary

When PHPT tests are run with code coverage, PHPUnit 13.4.0 to 13.4.3 writes the code of each PHPT test to a directory with a fixed name below the operating system's path used for temporary files, for instance `/tmp/phpunit-phpt` on Linux, and executes it from there. PHPUnit uses this directory even when it was created by another user.

On a system where the path used for temporary files is shared between users, another local user can create this directory before the developer runs PHPUnit, replace the code of a PHPT test before it is executed, and thereby execute arbitrary code with the privileges of the developer. The test still passes and the code coverage report is complete, so the attack is not visible.

The impact is full code execution as the user who runs PHPUnit. The likelihood is low: the attacker needs an account on the same system and must create the directory before the developer runs PHPT tests with code coverage. macOS and Windows use per-user temporary directories by default and are not affected in their default configuration. PHPUnit 12.5 and earlier are not affected.

### Details

When code coverage is collected for a PHPT test, PHPUnit writes two temporary files: a `.php` file with the code of the PHPT test (the "job" file), which the child process executes, and a `.coverage` file, to which the child process writes the code coverage data it collected.

Since PHPUnit 13.4.0, these files are created in a directory with a fixed name:

* [`TestCase…