Versions 0.3.17 and earlier of marked has Four regexes were vulnerable
to catastrophic backtracking. This leaves markdown servers open to a
potential REDOS attack.
Coverage remained the same at 100.0% when pulling aa96bfcbc27763584fec43d31c853d016d06e2e0 on WS-2019-0027 into becb3ddf1f98d3efe6089e4ba90953637ad8897e on master.