To report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure.
None of the jsdom projects consider the so-called "ReDOS" family of "vulnerabilities" to be security problems.
The jsdom projects, by their nature, accept complicated inputs, as they are attempting to emulate a web browser. The fact that performance on some inputs can be slower than others is a natural consequence of this. We do not support running them without pre-vetting your inputs to be sure that they will cause acceptable performance for your use case. And as such, we do not recognize it as a security vulnerability if certain inputs trigger longer regular expression execution times.
If you would like to improve performance on certain inputs, a pull request will be accepted. But no security bounties or CEVs will be issued for these performance issues.
You can read more about ReDOS in the article "ReDOS 'vulnerabilities' and misaligned incentives".