Fix reflected XSS in echo_jwt and harden JWT handling#7
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- HTML-escape the reflected token and decoded payload (closes unauthenticated
reflected XSS on all UI-extension routes)
- Pin jwt.decode algorithms=["HS256"] to prevent algorithm confusion
- Use hmac.compare_digest for the X-Perc-App-Secret comparison
- Default app.run to debug=False, opt-in via FLASK_DEBUG
- Use request.path instead of base_url.split("/")[-1]
- Bump python-jose (CVE-2024-33663, CVE-2024-33664) and Flask off the 2019
pins, which also fail to import on Python >= 3.10
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Fix reflected XSS in
/echo_jwtand harden JWT handlingWhat & why
The
jwtquery parameter is interpolated into the HTML response viastr.format()with no escaping. Since a returned string is served astext/html, any markup in the parameter executes in the browser. Theinvalid-token branch requires no secret, so this is an unauthenticated reflected XSS on all seven UI-extension routes:
Changes
tokenand the decoded payload withmarkupsafe.escape(closes the XSS).jwt.decode(..., algorithms=["HS256"])so the token's ownalgheadercan't select the algorithm (CWE-327 / the CVE-2024-33663 class of bug).
X-Perc-App-Secretheader withhmac.compare_digestinstead of!=(constant-time).app.runtodebug=False, opt-in viaFLASK_DEBUG— the READMEinstructs exposing this via ngrok, and
debug=Trueexposes the Werkzeugdebugger (RCE).
request.pathinstead ofrequest.base_url.split("/")[-1]for thecallback name.
python-jose(CVE-2024-33663, CVE-2024-33664) and Flask off the 2019pins, which also don't import on Python >= 3.10 (
from collections import Mapping).