Monte Carlo simulations are an important tool in modern physics experiments. With improving detector sensitivities, higher accuracies are also required from simulations, for example in reconstruction tasks. This includes both correctness from a physical as well as an algorithmic point of view. PROPOSAL is a Monte Carlo simulation framework that provides three-dimensional simulations of high-energy photons, electrons, muons, and taus. It is written in C++, but can also be used within Python via a wrapper. The structure of the software allows for simple customization of the propagation environment, physics descriptions, or precision settings for a variety of use cases. Examples are the application in neutrino observatories, underground experiments, or air shower simulations. This contribution focuses on the recent physics updates of the framework, describing the methodology and implication of these improvements. In particular, this involves effects at the higher and lower end of the energy scale covered by PROPOSAL. For high-energy photons, photon-nucleon interactions, muon pairproduction, and the Landau-Pomeranchuk-Migdal effect in electron-positron pairproduction are now included. As lower-energy effects, the deflection of muons in stochastic interactions as well as an approximate description of the photoeffect for photons have been implemented.