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PYSEC-2020-238

Details

AuthRestServlet in Matrix Synapse before 1.21.0 is vulnerable to XSS due to unsafe interpolation of the session GET parameter. This allows a remote attacker to execute an XSS attack on the domain Synapse is hosted on, by supplying the victim user with a malicious URL to the /_matrix/client/r0/auth/*/fallback/web or /_matrix/client/unstable/auth/*/fallback/web Synapse endpoints.

Are you affected?

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Affected packages

PyPI / matrix-synapse

Introduced in: 0 Fixed in: 1.21.0

Fix pip install --upgrade 'matrix-synapse>=1.21.0'

References

https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory [ADVISORY]
https://github.com/matrix-org/synapse/pull/8444 [WEB]
https://github.com/matrix-org/synapse/releases/tag/v1.21.2 [WEB]
https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq [ADVISORY]