Several quadratic complexity bugs may lead to denial of service in Commonmarker
## Impact
Several quadratic complexity bugs in commonmarker's underlying `cmark-gfm`
https://github.com/github/cmark-gfm library may lead to unbounded resource exhaustion and subsequent denial of service.
The following vulnerabilities were addressed:
* CVE-2023-22483
https://github.com/github/cmark-gfm/security/advisories/GHSA-29g3-96g3-jg6c
* CVE-2023-22484
https://github.com/github/cmark-gfm/security/advisories/GHSA-24f7-9frr-5h2r
* CVE-2023-22485
https://github.com/github/cmark-gfm/security/advisories/GHSA-c944-cv5f-hpvr
* CVE-2023-22486
https://github.com/github/cmark-gfm/security/advisories/GHSA-r572-jvj2-3m8p
For more information, consult the release notes for version `0.23.0.gfm.7`
https://github.com/github/cmark-gfm/releases/tag/0.29.0.gfm.7.
## Mitigation
Users are advised to upgrade to commonmarker version `0.23.7`
https://rubygems.org/gems/commonmarker/versions/0.23.7.