CodeQL, a semantic code analysis engine and query tool for finding security vulnerabilities across a codebase, has been made available for free by GitHub for anyone to use in research or to analyze open source code.
CodeQL queries code as if it were data. Developers can use CodeQL to write a query that finds all variants of a vulnerability, and then share that query with other developers. For example, a developer could create a query that mimics a bug class for cross-site scripting, then use that query to find any bug class. CodeQL also can be used to find zero days, variants of critical vulnerabilities, and defects such as buffer overflows or SQL injection issues.