WASM, famous from web browsers, regularly sees breaking out of sandbox issues. For example, see WebAssembly notes here:
Often these issues may lead to arbitrary code execution, the most dangerous kind of issue. These are especially prone with just-in-time WASM code interpretation, as the attacker has a lot of control over produced binary code. In the case of EOS, this would be malicious smart contract code. Also, we have similar cases over the history of Java JVM that allowed executing sandboxed Java code to allow to escape into host OS.
Now 360 (Chinese Internet company) claims that they have found arbitrary code execution in EOS:
What safety measures, like process isolation, EOS takes to ensure that the future arbitrary code execution or sandbox escapes in WASM don't allow taking over the block producer?