{"id":"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.","aliases":["CVE-2020-26891","GHSA-3x8c-fmpc-5rmq"],"modified":"2023-11-08T04:03:20.342815Z","published":"2020-10-19T17:15:00Z","references":[{"type":"ADVISORY","url":"https://matrix.org/blog/2020/10/15/synapse-1-21-2-released-and-security-advisory"},{"type":"WEB","url":"https://github.com/matrix-org/synapse/pull/8444"},{"type":"WEB","url":"https://github.com/matrix-org/synapse/releases/tag/v1.21.2"},{"type":"ADVISORY","url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-3x8c-fmpc-5rmq"}],"affected":[{"package":{"name":"matrix-synapse","ecosystem":"PyPI","purl":"pkg:pypi/matrix-synapse"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.21.0"}]}],"versions":["0.33.5","0.33.5.1","0.33.6","0.33.6rc1","0.33.7","0.33.7rc1","0.33.7rc2","0.33.8","0.33.8rc2","0.33.9","0.34.0","0.34.0.1","0.34.0rc1","0.34.0rc2","0.34.1.1","0.99.0","0.99.0rc1","0.99.0rc2","0.99.0rc3","0.99.0rc4","0.99.1","0.99.1.1","0.99.1rc1","0.99.1rc2","0.99.2","0.99.2rc1","0.99.3","0.99.3.1","0.99.3.2","0.99.3rc1","0.99.4","0.99.4rc1","0.99.5","0.99.5.1","0.99.5.2","0.99.5rc1","1.0.0","1.0.0rc1","1.0.0rc2","1.0.0rc3","1.1.0","1.1.0rc1","1.1.0rc2","1.10.0","1.10.0rc1","1.10.0rc2","1.10.0rc3","1.10.0rc5","1.10.1","1.11.0","1.11.0rc1","1.11.1","1.12.0","1.12.0rc1","1.12.1","1.12.1rc1","1.12.2","1.12.3","1.12.4","1.12.4rc1","1.13.0","1.13.0rc1","1.13.0rc2","1.13.0rc3","1.14.0","1.14.0rc1","1.14.0rc2","1.15.0","1.15.0rc1","1.15.1","1.15.2","1.16.0","1.16.0rc1","1.16.0rc2","1.16.1","1.17.0","1.17.0rc1","1.18.0","1.18.0rc1","1.18.0rc2","1.19.0","1.19.0rc1","1.19.1","1.19.1rc1","1.19.2","1.19.3","1.2.0","1.2.0rc1","1.2.0rc2","1.2.1","1.20.0","1.20.0rc1","1.20.0rc2","1.20.0rc3","1.20.0rc4","1.20.0rc5","1.20.1","1.21.0rc1","1.21.0rc2","1.21.0rc3","1.3.0","1.3.0rc1","1.3.1","1.4.0","1.4.0rc1","1.4.0rc2","1.4.1","1.4.1rc1","1.5.0","1.5.0rc1","1.5.0rc2","1.5.1","1.6.0","1.6.0rc1","1.6.0rc2","1.6.1","1.7.0","1.7.0rc1","1.7.0rc2","1.7.1","1.7.2","1.7.3","1.8.0","1.8.0rc1","1.9.0","1.9.0.dev1","1.9.0.dev2","1.9.0rc1","1.9.1"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/matrix-synapse/PYSEC-2020-238.yaml"}}],"schema_version":"1.7.3"}