9701fd32b7
Based on @walle303's work at https://github.com/matrix-org/matrix-react-sdk/pull/1820 Deliberately reverts https://github.com/matrix-org/matrix-react-sdk/commit/8f778f54fd10428836c99d08346cf89f038dd0ce Mitigates XSS by whitelisting the mime-types of the attachments so that malicious ones should not be recognised and executed by the browser.