Fix CVE-2018-12356 by hardening the regex.
Fix CVE-2018-12356 by hardening the regex.

fixes and closes #219


Former-commit-id: 2ae1d90723af8ebbe8df0f091ebe336da280914c
syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin