diff --git a/packages/client/src/components/MkDialog.vue b/packages/client/src/components/MkDialog.vue
index 5acef39654..3631375c8c 100644
--- a/packages/client/src/components/MkDialog.vue
+++ b/packages/client/src/components/MkDialog.vue
@@ -54,7 +54,8 @@
 				<Mfm :text="i18n.ts.password" />
 			</header>
 			<div v-if="text" :class="$style.text">
-				<Mfm :text="text" />
+				<span v-if="isPlaintext === true">{{ text }}</span>
+				<Mfm v-else :text="text" />
 			</div>
 			<MkInput
 				v-if="input && input.type !== 'paragraph'"
@@ -245,6 +246,7 @@ const props = withDefaults(
 			| "search";
 		title: string;
 		text?: string;
+		isPlaintext?: boolean;
 		input?: Input;
 		select?: Select;
 		icon?: string;
@@ -268,6 +270,7 @@ const props = withDefaults(
 		isYesNo: false,
 
 		cancelableByBgClick: true,
+		isPlaintext: false,
 	},
 );
 
diff --git a/packages/client/src/components/MkMedia.vue b/packages/client/src/components/MkMedia.vue
index 7607ed2980..fb0c181a00 100644
--- a/packages/client/src/components/MkMedia.vue
+++ b/packages/client/src/components/MkMedia.vue
@@ -138,6 +138,7 @@ function captionPopup() {
 	os.alert({
 		type: "info",
 		text: props.media.comment,
+		isPlaintext: true,
 	});
 }
 
diff --git a/packages/client/src/os.ts b/packages/client/src/os.ts
index 1943059298..0e74ff741b 100644
--- a/packages/client/src/os.ts
+++ b/packages/client/src/os.ts
@@ -277,6 +277,7 @@ export function alert(props: {
 	type?: "error" | "info" | "success" | "warning" | "waiting" | "question";
 	title?: string | null;
 	text?: string | null;
+	isPlaintext?: boolean;
 }): Promise<void> {
 	return new Promise((resolve, reject) => {
 		if (props.text == null && props.type === "error") {
@@ -301,6 +302,7 @@ export function confirm(props: {
 	text?: string | null;
 	okText?: string;
 	cancelText?: string;
+	isPlaintext?: boolean;
 }): Promise<{ canceled: boolean }> {
 	return new Promise((resolve, reject) => {
 		popup(
@@ -323,6 +325,7 @@ export function yesno(props: {
 	type: "error" | "info" | "success" | "warning" | "waiting" | "question";
 	title?: string | null;
 	text?: string | null;
+	isPlaintext?: boolean;
 }): Promise<{ canceled: boolean }> {
 	return new Promise((resolve, reject) => {
 		popup(