Injection

Injection is the act of introducing a substance into a system, organism, or process. The term is used across fields such as medicine, manufacturing, and computer science, and each context has its own methods and risks.

In medicine, injections deliver liquids such as vaccines, medications, or contrast agents into the body. Routes include intramuscular, subcutaneous, intravenous, and intradermal administration, each with specific indications and onset times. Proper technique, sterile equipment, and dose accuracy are essential, and injections carry risks such as infection, allergic reaction, and tissue damage.

In computing, injection refers to exploiting software vulnerabilities where untrusted input is treated as part of a query, command, or code. Notable forms include SQL injection, which inserts or manipulates database queries; code injection, which injects executable code; and command injection, which runs system commands. Attacks exploit unsanitized input, insufficient validation, or insecure privileges. Countermeasures include input validation, parameterized queries or prepared statements, least privilege, and input sanitization.

Other common uses include injection molding in plastics manufacturing and fuel injection in internal combustion engines. These processes deliver precise amounts of material to achieve desired properties or performance.