Impact Given a malformed "{% case %}" tag without associated "{% when %}" or "{% else %}" block, and no terminating "{% endcase %}" tag, Python Liquid hangs in an infinite loop at parse time. This allows malicious template authors to craft templates for a denial of service attack. Patches The issue is fixed in version 2.2.1 with the correction of the "liquid.TokenStream.eof" attribute. The "kind" and "value" of the special EOF token are now the same, so either can be tested against "liquid.token.TOKEN_EOF". Workarounds Manually correct the definition of "liquid.TokenStream.eof" before parsing any templates. import liquid from liquid.token import TOKEN_EOF liquid.stream.TokenStream.eof = liquid.Token(TOKEN_EOF, TOKEN_EOF, -1, "") ...