An arbitrary file overwrite is a security flaw where a program can replace a file it should not be able to modify. The target may be chosen by an attacker, or the software may be tricked into writing outside its intended directory. This is especially dangerous when the overwritten file is a configuration file, script, or command wrapper, because even a single changed file can alter how a system behaves.
In cyber security, this issue matters because it breaks integrity rather than confidentiality. Attackers may use it to plant malicious code, disable protections, or redirect commands during package installation, archive extraction, or file upload handling. Defenders look for strict path validation, safe filename handling, and permission checks that ensure writes stay inside approved locations. In package managers and build pipelines, untrusted metadata should never directly control filesystem paths or output files.