PyMdown Extensions is a set of extensions for the "Python-Markdown" markdown project. Versions prior to 10.16.1 have a ReDOS bug found within the figure caption extension ("pymdownx.blocks.caption"). In systems that take unchecked user content, this could cause long hanges when processing the data if a malicious payload was crafted. This issue is patched in Release 10.16.1. As a workaround, those who process unknown user content without timeouts or other safeguards in place to prevent really large, malicious content being aimed at systems may avoid the use of "pymdownx.blocks.caption" until they're able to upgrade.