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[Security] Fix CodeQL alert #27: XML external entity expansion #85

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[Security] Fix CodeQL alert #27: XML external entity expansion #85

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4 changes: 2 additions & 2 deletions vulnerable_xxe.py
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
import xml.etree.ElementTree as ET
from flask import Flask, request
from lxml import etree
import defusedxml.lxml as defused_lxml
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@cursor cursor Bot Mar 26, 2026

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Fix uses deprecated module marked for removal

Medium Severity

The defusedxml.lxml module is officially deprecated by its maintainer and marked for removal in a future release. Importing it emits a DeprecationWarning at runtime. The maintainer notes it was only "example code" and explicitly states it has "NO protection against decompression bombs." Since lxml itself now includes built-in mitigations (disabled network access, billion-laughs protection), the recommended approach is to configure etree.XMLParser directly with safe settings like resolve_entities=False and no_network=True.

Additional Locations (1)
Fix in Cursor Fix in Web

import xml.sax

app = Flask(__name__)
Expand All @@ -17,8 +18,7 @@ def parse_xml():
def process_xml():
xml_content = request.data.decode()

parser = etree.XMLParser()
doc = etree.fromstring(xml_content.encode(), parser)
doc = defused_lxml.fromstring(xml_content.encode())

return etree.tostring(doc).decode()

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