Hi all,
Heads up that we made an emergency release of Riot/Web 0.13.5 a few hours ago to fix a XSS vulnerability found and reported by walle303 - many thanks for disclosing it responsibly.
Please upgrade to Riot/Web 0.13.5 asap. If you're using riot.im/app or riot.im/develop this simply means hitting Refresh; otherwise please upgrade your Riot deployment as soon as possible. Alpine, Debian and Fedora/RPM packages are already updated - huge thanks to the maintainers for the fast turnaround.
The issue lies in the relatively obscure external_url feature, which lets bridges specify a URL for bridged events, letting Riot/Web users link through to the 'original' event (e.g. a twitter URL on a bridged tweet). The option is hidden in a context menu and labelled "Source URL", and is only visible on events which have the external_url field set. Unfortunately Riot/Web didn't sanitise the URL correctly, allowing a malicious URL to be injected - and this has been the case since the feature landed in Riot 0.9.0 (Nov 2016).
If you're not able to upgrade to Riot/Web 0.13.5 for some reason, then please do not click on the 'Source URL' feature on the event context menu:
Apologies for the inconvenience,
thanks,
Matthew
The Foundation needs you
The Matrix.org Foundation is a non-profit and only relies on donations to operate. Its core mission is to maintain the Matrix Specification, but it does much more than that.
It maintains the matrix.org homeserver and hosts several bridges for free. It fights for our collective rights to digital privacy and dignity.
Support us