A diff is a comparison view that shows what changed between two versions of a file, commit, or repository state. It can highlight added, removed, or modified lines, and in code platforms it may also render structured formats such as notebooks, JSON, or markup into a readable review view.
In cybersecurity, diffs matter because they are not just display tools: they often trigger server-side parsing, rendering, and normalization logic. That makes them part of the attack surface. If a platform processes attacker-controlled content while generating a diff, a flaw in the parser or renderer can lead to crashes, data exposure, or even command execution. Defenders review diff paths carefully, especially for complex file types, and limit privileges, patch quickly, and treat review features as security-critical backend functions rather than harmless UI.