Merge commit from fork

* SP-2025-03.1 always wrap icon&thumbnail URLs

if they're not HTTP URLs, the frontend won't be able to display them
anyway (`<img src="mailto:…">` or '<div stile="background-image:
url(nntp:…)">` aren't going to work!), so let's always run them through the
media proxy, which will fail harder (fetching a `javascript:` URL
won't do anything in the backend, might do something in the frontend)
and will always protect the client's address in cases like `gemini:`
where the browser could try to fetch

* SP-2025-03.2 use object binding for more styles

interpolating a random (remote-controlled!) string into a `style`
attribute is a bad idea; using VueJS object binding, we should get
proper quoting and therefore safe parse failures instead of CSS
injections / XSS

* SP-2025-03.3 slightly more robust "self" URL handling

parse URLs instead of treating them as strings; this is still not
perfect, but the `URL` class only handles full URLs, not relative
ones, so there's so way to ask it "give me a URL object that
represents this resource relative to this base URL"

notice that passing very weird URLs to `MkUrl` and `MkUrlPreview` will
break the frontend (in dev mode) because there's an untrapped `new
URL(…)` that may explode; production builds seem to safely ignore the
error, though

---------

Co-authored-by: dakkar <dakkar@thenautilus.net>

6 files changed, 16 insertions, 10 deletions

diff --git a/packages/frontend/src/components/MkLink.vue b/packages/frontend/src/components/MkLink.vue
index 4bac2bcea4..4cbf289448 100644
--- a/packages/frontend/src/components/MkLink.vue
+++ b/packages/frontend/src/components/MkLink.vue
@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <component
-	:is="self ? 'MkA' : 'a'" ref="el" style="word-break: break-all;" class="_link" :[attr]="self ? url.substring(local.length) : url" :rel="rel ?? 'nofollow noopener'" :target="target"
+	:is="self ? 'MkA' : 'a'" ref="el" style="word-break: break-all;" class="_link" :[attr]="maybeRelativeUrl" :rel="rel ?? 'nofollow noopener'" :target="target"
 	:behavior="props.navigationBehavior"
 	:title="url"
 >
@@ -21,6 +21,7 @@ import { useTooltip } from '@/use/use-tooltip.js';
 import * as os from '@/os.js';
 import { isEnabledUrlPreview } from '@/instance.js';
 import type { MkABehavior } from '@/components/global/MkA.vue';
+import { maybeMakeRelative } from '@@/js/url.js';
 
 const props = withDefaults(defineProps<{
 	url: string;
@@ -29,7 +30,8 @@ const props = withDefaults(defineProps<{
 }>(), {
 });
 
-const self = props.url.startsWith(local);
+const maybeRelativeUrl = maybeMakeRelative(props.url, local);
+const self = maybeRelativeUrl !== props.url;
 const attr = self ? 'to' : 'href';
 const target = self ? null : '_blank';
 
diff --git a/packages/frontend/src/components/MkUrlPreview.vue b/packages/frontend/src/components/MkUrlPreview.vue
index 20dab6f028..71c8a6a6e8 100644
--- a/packages/frontend/src/components/MkUrlPreview.vue
+++ b/packages/frontend/src/components/MkUrlPreview.vue
@@ -44,8 +44,8 @@ SPDX-License-Identifier: AGPL-3.0-only
 	</div>
 </template>
 <div v-else>
-	<component :is="self ? 'MkA' : 'a'" :class="[$style.link, { [$style.compact]: compact }]" :[attr]="self ? url.substring(local.length) : url" rel="nofollow noopener" :target="target" :title="url">
-		<div v-if="thumbnail && !sensitive" :class="$style.thumbnail" :style="prefer.s.dataSaver.urlPreview ? '' : `background-image: url('${thumbnail}')`">
+	<component :is="self ? 'MkA' : 'a'" :class="[$style.link, { [$style.compact]: compact }]" :[attr]="maybeRelativeUrl" rel="nofollow noopener" :target="target" :title="url">
+		<div v-if="thumbnail && !sensitive" :class="$style.thumbnail" :style="prefer.s.dataSaver.urlPreview ? '' : { backgroundImage: `url('${thumbnail}')` }">
 		</div>
 		<article :class="$style.body">
 			<header :class="$style.header">
@@ -94,6 +94,7 @@ import MkButton from '@/components/MkButton.vue';
 import { transformPlayerUrl } from '@/utility/player-url-transform.js';
 import { store } from '@/store.js';
 import { prefer } from '@/preferences.js';
+import { maybeMakeRelative } from '@@/js/url.js';
 
 type SummalyResult = Awaited<ReturnType<typeof summaly>>;
 
@@ -111,7 +112,8 @@ const props = withDefaults(defineProps<{
 const MOBILE_THRESHOLD = 500;
 const isMobile = ref(deviceKind === 'smartphone' || window.innerWidth <= MOBILE_THRESHOLD);
 
-const self = props.url.startsWith(local);
+const maybeRelativeUrl = maybeMakeRelative(props.url, local);
+const self = maybeRelativeUrl !== props.url;
 const attr = self ? 'to' : 'href';
 const target = self ? null : '_blank';
 const fetching = ref(true);
diff --git a/packages/frontend/src/components/MkUserInfo.vue b/packages/frontend/src/components/MkUserInfo.vue
index cff531b2ca..69144d3824 100644
--- a/packages/frontend/src/components/MkUserInfo.vue
+++ b/packages/frontend/src/components/MkUserInfo.vue
@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <div class="_panel" :class="$style.root">
-	<div :class="$style.banner" :style="user.bannerUrl ? `background-image: url(${prefer.s.disableShowingAnimatedImages ? getStaticImageUrl(user.bannerUrl) : user.bannerUrl})` : ''"></div>
+	<div :class="$style.banner" :style="user.bannerUrl ? { backgroundImage: `url(${prefer.s.disableShowingAnimatedImages ? getStaticImageUrl(user.bannerUrl) : user.bannerUrl})` } : ''"></div>
 	<MkAvatar :class="$style.avatar" :user="user" indicator/>
 	<div :class="$style.title">
 		<MkA :class="$style.name" :to="userPage(user)"><MkUserName :user="user" :nowrap="false"/></MkA>
diff --git a/packages/frontend/src/components/MkUserPopup.vue b/packages/frontend/src/components/MkUserPopup.vue
index 17a882a3a6..3bd2a2ffae 100644
--- a/packages/frontend/src/components/MkUserPopup.vue
+++ b/packages/frontend/src/components/MkUserPopup.vue
@@ -13,7 +13,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 >
 	<div v-if="showing" :class="$style.root" class="_popup _shadow" :style="{ zIndex, top: top + 'px', left: left + 'px' }" @mouseover="() => { emit('mouseover'); }" @mouseleave="() => { emit('mouseleave'); }">
 		<div v-if="user != null">
-			<div :class="$style.banner" :style="user.bannerUrl ? `background-image: url(${prefer.s.disableShowingAnimatedImages ? getStaticImageUrl(user.bannerUrl) : user.bannerUrl})` : ''">
+			<div :class="$style.banner" :style="user.bannerUrl ? { backgroundImage: `url(${prefer.s.disableShowingAnimatedImages ? getStaticImageUrl(user.bannerUrl) : user.bannerUrl})` } : ''">
 				<span v-if="$i && $i.id != user.id && user.isFollowed" :class="$style.followed">{{ i18n.ts.followsYou }}</span>
 			</div>
 			<svg viewBox="0 0 128 128" :class="$style.avatarBack">
diff --git a/packages/frontend/src/components/MkUserSetupDialog.User.vue b/packages/frontend/src/components/MkUserSetupDialog.User.vue
index 4accc6183b..54887ba0f0 100644
--- a/packages/frontend/src/components/MkUserSetupDialog.User.vue
+++ b/packages/frontend/src/components/MkUserSetupDialog.User.vue
@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <div v-adaptive-bg class="_panel" style="position: relative;">
-	<div :class="$style.banner" :style="user.bannerUrl ? `background-image: url(${user.bannerUrl})` : ''"></div>
+	<div :class="$style.banner" :style="user.bannerUrl ? { backgroundImage: `url(${user.bannerUrl})` } : ''"></div>
 	<MkAvatar :class="$style.avatar" :user="user" indicator/>
 	<div :class="$style.title">
 		<div :class="$style.name"><MkUserName :user="user" :nowrap="false"/></div>
diff --git a/packages/frontend/src/components/global/MkUrl.vue b/packages/frontend/src/components/global/MkUrl.vue
index 0c248b041d..49f716d886 100644
--- a/packages/frontend/src/components/global/MkUrl.vue
+++ b/packages/frontend/src/components/global/MkUrl.vue
@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <component
-	:is="self ? 'MkA' : 'a'" ref="el" :class="$style.root" class="_link" :[attr]="self ? props.url.substring(local.length) : props.url" :rel="rel ?? 'nofollow noopener'" :target="target"
+	:is="self ? 'MkA' : 'a'" ref="el" :class="$style.root" class="_link" :[attr]="maybeRelativeUrl" :rel="rel ?? 'nofollow noopener'" :target="target"
 	:behavior="props.navigationBehavior"
 	@contextmenu.stop="() => {}"
 >
@@ -32,6 +32,7 @@ import * as os from '@/os.js';
 import { useTooltip } from '@/use/use-tooltip.js';
 import { isEnabledUrlPreview } from '@/instance.js';
 import type { MkABehavior } from '@/components/global/MkA.vue';
+import { maybeMakeRelative } from '@@/js/url.js';
 
 function safeURIDecode(str: string): string {
 	try {
@@ -50,7 +51,8 @@ const props = withDefaults(defineProps<{
 	showUrlPreview: true,
 });
 
-const self = props.url.startsWith(local);
+const maybeRelativeUrl = maybeMakeRelative(props.url, local);
+const self = maybeRelativeUrl !== props.url;
 const url = new URL(props.url);
 if (!['http:', 'https:'].includes(url.protocol)) throw new Error('invalid url');
 const el = ref();