CliInvoke is a .NET library for invoking command-line programs, and its "CliInvoke.Specializations" packages provide specialized wrappers for shells such as PowerShell and Windows Command Prompt. "CliInvoke.Specializations" versions 2.2.0 through 2.8.4, 2.9.0 through 2.9.3, 2.10.0 through 2.10.4, 3.0.0-alpha.1 through 3.0.0-alpha.4, and 3.0.0-alpha.8 through 3.0.0-alpha.10, as well as "AlastairLundy.CliInvoke.Specializations" versions 1.0.0-rc.1 through 1.6.1.1, contain an OS command injection vulnerability in their PowerShell and Cmd wrappers. The wrappers pass a caller-controlled target and arguments to "pwsh -Command" or "cmd /c" using a single "ProcessStartInfo.Arguments" string, allowing a double quote in untrusted input to break operating-system-level quoting and cause the shell to execute an additional command with the host process's privileges. The vulnerability is patched in "CliInvoke.Specializations" versions 2.8.5, 2.9.4, 2.10.5, and 3.0.0-beta.1, and in "AlastairLundy.CliInvoke.Specializations" version 2.0.2. No complete workaround is available; users unable to upgrade should reject or remove double quotes from target paths and arguments, additionally reject shell metacharacters in versions 2.2.0 through 2.9.2 and 3.0.0-alpha.1 through 3.0.0-alpha.4, or bypass the PowerShell and Cmd wrappers and invoke target processes directly when handling untrusted input.