diff --git a/.env b/.env
index 738f94d2..377beeb4 100644
--- a/.env
+++ b/.env
@@ -42,6 +42,9 @@ ADMIN_PASSWORD=test
 ADMIN_AUTH_BYPASS=false
 
 # Auth Realm for HTTP auth
+# Do not change this on an existing install: passwords created before v1.10.0, and any imported
+# from Baikal, are md5(username:AUTH_REALM:password), so changing the realm silently invalidates
+# every one of them. See the README.
 AUTH_REALM=SabreDAV
 
 # Auth Method for the frontend
diff --git a/README.md b/README.md
index 93a1416c..88a3626c 100644
--- a/README.md
+++ b/README.md
@@ -137,6 +137,29 @@ AUTH_METHOD=Basic # can be "Basic", "IMAP" or "LDAP"
 ```
 > See [the following paragraph](#specific-environment-variables-for-imap-and-ldap-authentication-methods) for more information if you choose either IMAP or LDAP.
 
+> [!WARNING]
+>
+> **Do not change `AUTH_REALM` on an existing installation.** Davis stored passwords as
+> `md5(username:AUTH_REALM:password)` until v1.10.0 (September 2021), and a database imported from
+> Baïkal uses the same scheme. The realm is part of those hashes, so changing it makes every one of
+> them stop working, with no error beyond a failed login — the accounts are still there, they simply
+> cannot authenticate any more.
+>
+> Passwords set since v1.10.0 use bcrypt and are unaffected. You can still be carrying legacy ones
+> without ever having used Baïkal, if the account predates that version. To find out:
+>
+> ```sql
+> SELECT username FROM users WHERE digesta1 NOT LIKE '$2y$%';
+> ```
+>
+> Any row returned is a legacy hash tied to the current realm.
+>
+> There is no password reset in Davis. If you must change the realm, the only way back is to open
+> each of those accounts in the dashboard and type a new password: the field is blank on the edit
+> page and leaving it blank keeps the current hash, so filling it in is what replaces it. The new
+> one is stored with bcrypt and no longer depends on the realm. Your own admin login is unaffected —
+> it comes from `ADMIN_LOGIN` / `ADMIN_PASSWORD`, not from the users table.
+
 **d. The global flags to enable CalDAV, CardDAV and WebDAV**. You can also disable the option to have calendars public
 
 ```shell
diff --git a/src/Plugins/DavisIMipPlugin.php b/src/Plugins/DavisIMipPlugin.php
index 0b0be0ee..66280f70 100644
--- a/src/Plugins/DavisIMipPlugin.php
+++ b/src/Plugins/DavisIMipPlugin.php
@@ -195,7 +195,9 @@ public function schedule(ITip\Message $itip)
             return $else;
         };
 
-        $url = $notEmpty('URL', false);
+        // The invitation renders this as a link, and it is whatever the organiser's client put in
+        // VEVENT.URL. Anything but a web or mail address is dropped rather than made clickable.
+        $url = $this->linkableUrl($notEmpty('URL', false));
         $description = $notEmpty('DESCRIPTION', false);
         $location = $notEmpty('LOCATION', false);
         $locationImageDataAsBase64 = false;
@@ -325,6 +327,22 @@ public function schedule(ITip\Message $itip)
         }
     }
 
+    /**
+     * @param string|false $url
+     *
+     * @return string|false the url if it is one a mail client should offer to open, false otherwise
+     */
+    private function linkableUrl($url)
+    {
+        if (!is_string($url) || '' === $url) {
+            return false;
+        }
+
+        $scheme = parse_url($url, PHP_URL_SCHEME);
+
+        return \in_array(strtolower((string) $scheme), ['http', 'https', 'mailto'], true) ? $url : false;
+    }
+
     /**
      * Returns a bunch of meta-data about the plugin.
      *
diff --git a/src/Services/BirthdayService.php b/src/Services/BirthdayService.php
index 108c3e3c..36530e51 100644
--- a/src/Services/BirthdayService.php
+++ b/src/Services/BirthdayService.php
@@ -232,10 +232,6 @@ public function buildDataFromContact(string $cardData): ?VCalendar
 
         $leapDay = (2 === (int) $dateParts['month']
                 && 29 === (int) $dateParts['date']);
-        if (null === $dateParts['year'] || $originalYear < 1970) {
-            $birthday = ($leapDay ? '1972-' : '1970-')
-                .$dateParts['month'].'-'.$dateParts['date'];
-        }
 
         if ($leapDay) {
             /* Sabre\VObject supports BYMONTHDAY only if BYMONTH
diff --git a/templates/_partials/delegate_row.html.twig b/templates/_partials/delegate_row.html.twig
index 48d6c280..f3a2e233 100644
--- a/templates/_partials/delegate_row.html.twig
+++ b/templates/_partials/delegate_row.html.twig
@@ -21,6 +21,6 @@
     <p class="mb-1">{{ "users.username"|trans }} : <code>{{ delegate.username }}</code></p>
     <small>{{ "users.uri"|trans }} : <code>{{ delegate.uri }}</code></small>
     <div class="btn-group btn-group-sm mt-3 d-flex d-lg-none" role="group">
-        <a href="#" data-bs-toggle="modal" data-bs-target="#deleteModal-delegates" data-href="{{ path('user_delegate_remove',{userId: userId, principalProxyId: has_write ? principalProxyWrite.id : principalProxyRead.id, delegateId: delegate.id})}}" data-flavour="delegates" class="btn btn-outline-danger flex-fill flex-shrink-1 delete-modal"><span class="d-none d-sm-inline">⚠&nbsp;</span>{{ "remove"|trans }}</a>
+        <a href="#" data-bs-toggle="modal" data-bs-target="#deleteModal-delegates" data-href="{{ path('user_delegate_remove',{userId: userId, principalProxyId: has_write ? principalProxyWrite.id : principalProxyRead.id, delegateId: delegate.id})}}" data-flavour="delegates" class="btn btn-outline-danger flex-fill flex-shrink-1"><span class="d-none d-sm-inline">⚠&nbsp;</span>{{ "remove"|trans }}</a>
     </div>
 </div>
diff --git a/templates/calendars/index.html.twig b/templates/calendars/index.html.twig
index 1de0a5c3..97cf6448 100644
--- a/templates/calendars/index.html.twig
+++ b/templates/calendars/index.html.twig
@@ -41,7 +41,7 @@
                     data-bs-toggle="modal" data-bs-target="#deleteModal-calendars"
                     data-href="{{ path('calendar_delete',{userId: userId, id: calendar.id})}}"
                     data-flavour="calendars"
-                    class="btn btn-sm btn-outline-danger ms-1 delete-modal"
+                    class="btn btn-sm btn-outline-danger ms-1"
                 >⚠ {{ "delete"|trans }}</a>
             </div>
         </div>
@@ -67,7 +67,7 @@
                 data-bs-toggle="modal" data-bs-target="#deleteModal-calendars"
                 data-href="{{ path('calendar_delete',{userId: userId, id: calendar.id})}}"
                 data-flavour="calendars"
-                class="btn btn-outline-danger delete-modal"
+                class="btn btn-outline-danger"
             >⚠ {{ "delete"|trans }}</a>
         </div>
     </div>
diff --git a/tests/Functional/Plugins/ImipPluginTest.php b/tests/Functional/Plugins/ImipPluginTest.php
index 5811ec20..106372e7 100644
--- a/tests/Functional/Plugins/ImipPluginTest.php
+++ b/tests/Functional/Plugins/ImipPluginTest.php
@@ -131,6 +131,42 @@ public function testANonMailtoRecipientIsLogged(): void
         $this->assertSame([], $mailer->sent);
     }
 
+    /**
+     * `VEVENT.URL` comes from whoever created the event and the invitation makes it clickable in
+     * the recipient's mail client, so only web and mail addresses get through.
+     *
+     * @dataProvider urls
+     */
+    public function testOnlyLinkableUrlsReachTheInvitation(string $url, bool $expected): void
+    {
+        $logs = [];
+        $plugin = $this->plugin($mailer = $this->mailer(null), $logs);
+
+        $message = $this->message();
+        $message->message->VEVENT->add('URL', $url);
+        $plugin->schedule($message);
+
+        $this->assertCount(1, $mailer->sent);
+
+        // The templates render from this context, and both of them only emit a link when it is set
+        $this->assertSame(
+            $expected ? $url : false,
+            $mailer->sent[0]->getContext()['url'],
+            $url.($expected ? ' should be offered' : ' should not be offered')
+        );
+    }
+
+    public static function urls(): iterable
+    {
+        yield 'https' => ['https://example.org/meeting', true];
+        yield 'http' => ['http://example.org/meeting', true];
+        yield 'mailto' => ['mailto:someone@example.org', true];
+        yield 'javascript' => ['javascript:alert(1)', false];
+        yield 'data' => ['data:text/html,<script>alert(1)</script>', false];
+        yield 'file' => ['file:///etc/passwd', false];
+        yield 'no scheme' => ['example.org/meeting', false];
+    }
+
     public function testASuccessfulSendIsLoggedAndReported(): void
     {
         $logs = [];