cmark-gfm Quadratic complexity bugs may lead to a denial of service

cmark-gfm is GitHub's fork of cmark, a CommonMark parsing and rendering library and program in C. Versions prior to 0.29.0.gfm.7 are subject to several polynomial time complexity issues in cmark-gfm that may lead to unbounded resource exhaustion and subsequent denial of service. Various commands, when piped to cmark-gfm with large values, cause the running time to increase quadratically. These vulnerabilities have been patched in version 0.29.0.gfm.7.