Security of Julia, since possible to change the compiler at runtime

[Palli]

Continuing the discussion from This month in Julia World - 2026-08:

@jakobnissen

• security researcher Tsi-Lin Ng and others managed to backdoor the infrastructure behind the package managers for Python, Go, Flutter, and … Julia.
  He gave a presentation on the exploit at Black Hat 2026, the slides for which are publicly available.
  Rebuilding the Julia infrastructure to fix the issue took extra time since

Slide 48

Not too surprising. If you have access to the compiler (or infrastructure), then you can change the generated code:

Reflections on Trusting Trust

We can already change the parser at runtime. I believe we can also change the compiler in arbitrary ways. E.g. a package could?

Is there any way around this in Julia or languages like Lisp? Even Python? Can and should the compiler be code that is is a separate process? An .so/.dll? could you still unload it and load a new one from the REPL?

[dilumaluthge]

Hmmm. As soon as you load a package, its __init__() function runs, which can run arbitrary code, right? So a malicious package can just run malicious code in __init__() - no need to change the compiler.