Html tags are incorrectly parsed
According to the spec at https://developer.gnome.org/notification-spec/, notification servers should support the following html tags or otherwise strip them: b, i, u, a, img.
Unfortunately, "a" and "img" tags are neither supported nor stripped, leaving the html markup in the notification body.
I'm not sure if this is the right place to post this issue since the notification-daemon is archived. Feel free to move it to any appropriate repo.