LuaTeX before 1.17.0 allows execution of arbitrary shell commands when compiling a TeX file obtained from an untrusted source. This occurs because luatex-core.lua lets the original io.popen be accessed. This also affects TeX Live before 2023 r66984 and MiKTeX before 23.5.
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.