Espruino before 1.99 allows attackers to cause a denial of service (application crash) and a potential Escalation of Privileges with a user crafted input file via a Buffer Overflow during syntax parsing, because strncat is misused.
https://github.com/espruino/Espruino/issues/1425
https://github.com/espruino/Espruino/files/2019220/test_4.txt
https://github.com/espruino/Espruino/files/2019216/test_2.txt
https://github.com/espruino/Espruino/files/2019210/test_0.txt
https://github.com/espruino/Espruino/commit/0a7619875bf79877907205f6bee08465b89ff10b