In XS 9.0.0 in Moddable SDK OS180329, there is a heap-based buffer overflow in fxBeginHost in xsAPI.c when called from fxRunDefine in xsRun.c, as demonstrated by crafted JavaScript code to xst.
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2019-16366.json"