An HTTP client is a component that sends requests to web servers and handles their responses. It may be part of an application, a programming language runtime, or a separate library. Clients commonly process response headers and data, and may also decompress content such as Brotli-encoded responses.
HTTP clients matter in cybersecurity because they can expose applications to untrusted data returned by remote servers. If a client passes compressed content to a vulnerable decoder, malformed data may cause memory corruption and, in some circumstances, enable code execution. Defenders should keep client libraries and their bundled dependencies updated, review settings that enable compression, and verify that running processes use patched versions.