diff --git a/changelog/unreleased/fix-notification-email-double-escape.md b/changelog/unreleased/fix-notification-email-double-escape.md
new file mode 100644
index 0000000000..ff06a645e4
--- /dev/null
+++ b/changelog/unreleased/fix-notification-email-double-escape.md
@@ -0,0 +1,9 @@
+Bugfix: Don't re-escape notification email vars for each recipient
+
+When a notification went to several recipients in one call (e.g. a group
+invite to a space), each recipient past the first got subjects and bodies
+with one extra layer of HTML escaping. escapeStringMap mutated its input
+map, and the recipient loop reused the same map across iterations. It now
+returns a new map.
+
+https://github.com/opencloud-eu/opencloud/issues/2804
diff --git a/services/notifications/pkg/email/email.go b/services/notifications/pkg/email/email.go
index c53511c30e..b511dd6b18 100644
--- a/services/notifications/pkg/email/email.go
+++ b/services/notifications/pkg/email/email.go
@@ -204,8 +204,9 @@ func validateMime(incipit []byte) bool {
 }
 
 func escapeStringMap(vars map[string]string) map[string]string {
-	for k := range vars {
-		vars[k] = html.EscapeString(vars[k])
+	escaped := make(map[string]string, len(vars))
+	for k, v := range vars {
+		escaped[k] = html.EscapeString(v)
 	}
-	return vars
+	return escaped
 }
diff --git a/services/notifications/pkg/email/email_test.go b/services/notifications/pkg/email/email_test.go
new file mode 100644
index 0000000000..01df4094f8
--- /dev/null
+++ b/services/notifications/pkg/email/email_test.go
@@ -0,0 +1,25 @@
+package email
+
+import "testing"
+
+// Regression for #2804: escapeStringMap used to mutate its input map, and the
+// recipient render loop reuses that map across iterations.
+func TestEscapeStringMapDoesNotMutateInput(t *testing.T) {
+	const raw = "Test & Demo"
+	input := map[string]string{"SpaceName": raw}
+
+	first := escapeStringMap(input)
+	second := escapeStringMap(input)
+
+	if got, want := first["SpaceName"], "Test & Demo"; got != want {
+		t.Errorf("first call: got %q, want %q", got, want)
+	}
+	if first["SpaceName"] != second["SpaceName"] {
+		t.Errorf("escapeStringMap not idempotent on shared input: first=%q second=%q",
+			first["SpaceName"], second["SpaceName"])
+	}
+	if input["SpaceName"] != raw {
+		t.Errorf("escapeStringMap mutated its input: got %q, want %q",
+			input["SpaceName"], raw)
+	}
+}