wire-webapp is the web version of Wire, an open-source messenger. A cross-site scripting vulnerability exists in wire-webapp prior to version 2021-06-01-production.0. If a user is instructed to open an image in a new tab (right click -> open in new tab, or copy the URL and paste it in the URL bar), an the image payload is executed on the domain hosting the app (app.wire.com). In particular, if an image contains malicious code in addition to the actual picture, this code is executed on app.wire.com. This allows the attacker to fully control the user account. The vulnerability was patched in version 2021-06-01-production.0. As a workaround, users should not try to open image URLs.