A shared codebase is one underlying set of source code reused across multiple products, apps, or browser extensions. Instead of each release being built independently, the same core logic is copied or repackaged with different names, branding, or minor features. In security terms, that matters because one design flaw, hidden function, or malicious routine can appear in many places at once.
Attackers and shady developers use shared codebases to scale quickly: they can publish many similar extensions, change only the storefront details, and keep the same behavior underneath. That can widen the blast radius of risky permissions, such as access to browsing activity or network requests. For defenders, shared code is a useful clue in code review and threat hunting because it can reveal linked campaigns, copied malware, or a common operator. When two “different” tools behave the same way, they may be the same software family in disguise.