Use SafeStrings for event_live_issues

src/pretix/base/models/event.py

@@ -1403,15 +1403,12 @@ class Event(EventMixin, LoggedModel):
 
         for mp in self.organizer.meta_properties.all():
             if mp.required and not self.meta_data.get(mp.name):
-                issues.append(
-                    ('<a {a_attr}>' + gettext('You need to fill the meta parameter "{property}".') + '</a>').format(
-                        property=mp.name,
-                        a_attr='href="%s#id_prop-%d-value"' % (
-                            reverse('control:event.settings', kwargs={'organizer': self.organizer.slug, 'event': self.slug}),
-                            mp.pk
-                        )
-                    )
-                )
+                issues.append(format_html(
+                    '<a href="{href}{href_hash}">{text}</a>',
+                    text=gettext('You need to fill the meta parameter "{property}".').format(property=mp.name),
+                    href=reverse('control:event.settings', kwargs={'organizer': self.organizer.slug, 'event': self.slug}),
+                    href_hash=f'#id_prop-{mp.pk}-value',
+                ))
 
         responses = event_live_issues.send(self)
         for receiver, response in sorted(responses, key=lambda r: str(r[0])):

src/pretix/control/templates/pretixcontrol/event/live.html

@@ -19,7 +19,7 @@
                         </p>
                         <ul>
                             {% for issue in issues %}
-                                <li>{{ issue|safe }}</li>
+                                <li>{{ issue }}</li>
                             {% endfor %}
                         </ul>
                     </div>
@@ -42,7 +42,7 @@
                         </p>
                         <ul>
                             {% for issue in issues %}
-                                <li>{{ issue|safe }}</li>
+                                <li>{{ issue }}</li>
                             {% endfor %}
                         </ul>
                     </div>