Marked is a markdown parser and compiler. Prior to version 4.0.10 the regular expression `block.def` may cause catastrophic backtracking against some strings and lead to a regular expression denial of service (ReDoS). Anyone who runs untrusted markdown through a vulnerable version of marked and does not use a worker with a time limit may be affected. This issue is patched in version 4.0.10. As a workaround avoid running untrusted markdown through marked or run marked on a worker thread and set a reasonable time limit to prevent draining resources.