When the directory containing the installer does not have sufficiently restrictive file permissions, an attacker can modify (or replace) the installer to execute malicious code.
An installer that loads or executes files using an unconstrained search path may be vulnerable to substitute files under control of an attacker being loaded or executed instead of the intended files.
When the installation directory does not have sufficiently restrictive file permissions, an attacker can modify files in the installation directory to cause execution of malicious code.