The CMS collaboration at CERN is happy to announce the release of its fourth batch of open data to the public. With this release, which brings the volume of its open data to more than 2 PB (or two million GB), CMS has now provided open access to 100% of its research data recorded in proton–proton collisions in 2010, in line with the collaboration's data-release policy. The release also includes several new data and simulation samples. The new release builds upon and expands the scope of the successful use of CMS open data in research and in education. In this release, CMS open data address the ever-growing application of machine learning (ML) to challenges in high-energy physics.