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Use Safe Defaults for lxml Parsers #25

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@pixeebot pixeebot bot commented May 17, 2025

This codemod configures safe parameter values when initializing lxml.etree.XMLParser, lxml.etree.ETCompatXMLParser, lxml.etree.XMLTreeBuilder, or lxml.etree.XMLPullParser. If parameters resolve_entities, no_network, and dtd_validation are not set to safe values, your code may be vulnerable to entity expansion attacks and external entity (XXE) attacks.

Parameters no_network and dtd_validation have safe default values of True and False, respectively, so this codemod will set each to the default safe value if your code has assigned either to an unsafe value.

Parameter resolve_entities has an unsafe default value of True. This codemod will set resolve_entities=False if set to True or omitted.

The changes look as follows:

  import lxml.etree

- parser = lxml.etree.XMLParser()
- parser = lxml.etree.XMLParser(resolve_entities=True)
- parser = lxml.etree.XMLParser(resolve_entities=True, no_network=False, dtd_validation=True)
+ parser = lxml.etree.XMLParser(resolve_entities=False)
+ parser = lxml.etree.XMLParser(resolve_entities=False)
+ parser = lxml.etree.XMLParser(resolve_entities=False, no_network=True, dtd_validation=False)
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Feedback | Community | Docs | Codemod ID: pixee:python/safe-lxml-parser-defaults

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pixeebot bot commented May 25, 2025

I'm confident in this change, and the CI checks pass, too!

If you see any reason not to merge this, or you have suggestions for improvements, please let me know!

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pixeebot bot commented May 26, 2025

Just a friendly ping to remind you about this change. If there are concerns about it, we'd love to hear about them!

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