Synapse is vulnerable to cross-site scripting (XSS) attacks. An attacker is able to inject and execute malicious script as the library does not escape loading of HTML files from the default Synapse template directory, allowing access to cookies and other browser data and access to other resources served on the same domain or parent domains.
github.com/matrix-org/synapse/commit/e54746bdf7d5c831eabe4dcea76a7626f1de73df
github.com/matrix-org/synapse/pull/9200
github.com/matrix-org/synapse/pull/9200
github.com/matrix-org/synapse/releases/tag/v1.27.0
github.com/matrix-org/synapse/security/advisories/GHSA-246w-56m2-5899
github.com/matrix-org/synapse/security/advisories/GHSA-246w-56m2-5899
lists.fedoraproject.org/archives/list/[email protected]/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/
security-tracker.debian.org/tracker/CVE-2021-21332