CVE-2023-26303: markdown-it-py Denial of Service vulnerability

The vulnerability stemmed from improper handling of null assertions in multiple rendering functions. The GitHub patch shows critical replacements of 'assert' statements with conditional checks in these functions. Assertions like 'assert token.children is not None' and 'assert token.attrs contains alt' could be forcibly failed with malicious input, triggering uncaught AssertionErrors and crashing the application. The functions were directly modified in the security fix commit to remove these dangerous assertions.