[gavinray]

  >  the attacker can embed whatever WASM payload they want into the file since the file will be “opened” by “execute this offset into the file”.

And then do what with it?

WASM physically cannot interact with the underlying host or perform I/O -- you need a WASI environment for that.

[ratorx]

Putting aside the WASM sandboxing (I’m not familiar enough with it to understand how sandboxing works) there’s a DoS vector at least. Even regexes have had many DoS issues, and I can’t imagine WASM being easier to sandbox for DoS risk.

[7373737373]

There exist Wasm interpreters capable of limiting the number of instructions executed.

[titzer]

Many can, even if they have JITs, e.g. Wasmtime. Failing that, it's not that hard to add bytecode instrumentation that will count instructions and terminate early. Some execution platforms that utilize Wasm just inject bytecode instrumentation into guest programs before sending them to the Wasm engine. It's relatively easy to do and not that much overhead.