Critical advisory for pybars3

Advisory overview

pybars3 through 0.9.7 contains a code injection vulnerability in pybars/_compiler.py that allows template authors to execute Python code via unescaped bracketed path segments. Attackers can supply Handlebars templates with crafted segments in helper or block arguments to break out of string literals and execute Python in the application process.

Related references

• https://github.com/vladko312/advisories/blob/702e98db9642ece70d9e2150076d8014ffec2db3/pybars3.md
• https://github.com/wbond/pybars3
• https://github.com/wbond/pybars3/blob/0.9.7/pybars/_compiler.py#L159-L160
• https://github.com/wbond/pybars3/issues/88
• https://www.vulncheck.com/advisories/pybars3-through-0.9.7-code-injection-via-bracketed-path-segments