diff --git a/src/controllers/write/topics.js b/src/controllers/write/topics.js
index 974e6d1734..fbf21e333b 100644
--- a/src/controllers/write/topics.js
+++ b/src/controllers/write/topics.js
@@ -7,6 +7,7 @@ const topics = require('../../topics');
 const privileges = require('../../privileges');
 
 const helpers = require('../helpers');
+const middleware = require('../../middleware/assert');
 const uploadsController = require('../uploads');
 
 const Topics = module.exports;
@@ -105,7 +106,11 @@ Topics.addThumb = async (req, res) => {
 	// Add uploaded files to topic zset
 	if (files && files.length) {
 		await Promise.all(files.map(async (fileObj) => {
-			await topics.thumbs.associate(req.params.tid, fileObj.path);
+			await topics.thumbs.associate({
+				id: req.params.tid,
+				path: fileObj.path || null,
+				url: fileObj.url,
+			});
 		}));
 	}
 };
@@ -124,6 +129,13 @@ Topics.migrateThumbs = async (req, res) => {
 };
 
 Topics.deleteThumb = async (req, res) => {
+	if (!req.body.path.startsWith('http')) {
+		await middleware.assert.path(req, res);
+		if (res.headersSent) {
+			return;
+		}
+	}
+
 	await checkThumbPrivileges({ tid: req.params.tid, uid: req.user.uid, res });
 	if (res.headersSent) {
 		return;
diff --git a/src/routes/write/topics.js b/src/routes/write/topics.js
index 4ea061e911..9203146588 100644
--- a/src/routes/write/topics.js
+++ b/src/routes/write/topics.js
@@ -37,7 +37,7 @@ module.exports = function () {
 	setupApiRoute(router, 'get', '/:tid/thumbs', [], controllers.write.topics.getThumbs);
 	setupApiRoute(router, 'post', '/:tid/thumbs', [multipartMiddleware, middleware.validateFiles, ...middlewares], controllers.write.topics.addThumb);
 	setupApiRoute(router, 'put', '/:tid/thumbs', [], controllers.write.topics.migrateThumbs);
-	setupApiRoute(router, 'delete', '/:tid/thumbs', [...middlewares, middleware.assert.path], controllers.write.topics.deleteThumb);
+	setupApiRoute(router, 'delete', '/:tid/thumbs', [...middlewares, middleware.checkRequired.bind(null, ['path'])], controllers.write.topics.deleteThumb);
 
 	return router;
 };
diff --git a/src/topics/thumbs.js b/src/topics/thumbs.js
index 4b56f454af..c3ddd5a0b4 100644
--- a/src/topics/thumbs.js
+++ b/src/topics/thumbs.js
@@ -32,23 +32,29 @@ Thumbs.get = async function (tids) {
 	let response = thumbs.map((thumbSet, idx) => thumbSet.map(thumb => ({
 		id: tids[idx],
 		name: path.basename(thumb),
-		url: path.join(nconf.get('upload_url'), thumb),
+		url: thumb.startsWith('http') ? thumb : path.join(nconf.get('upload_url'), thumb),
 	})));
 
 	({ thumbs: response } = await plugins.hooks.fire('filter:topics.getThumbs', { tids, thumbs: response }));
 	return singular ? response.pop() : response;
 };
 
-Thumbs.associate = async function (id, relativePath) {
+Thumbs.associate = async function ({ id, path: relativePath, url }) {
 	// Associates a newly uploaded file as a thumb to the passed-in draft or topic
 	const isDraft = validator.isUUID(String(id));
+	const value = relativePath || url;
 	const set = `${isDraft ? 'draft' : 'topic'}:${id}:thumbs`;
 	const numThumbs = await db.sortedSetCard(set);
-	relativePath = relativePath.replace(nconf.get('upload_path'), '');
-	db.sortedSetAdd(set, numThumbs, relativePath);
 
-	// Associate thumbnails with the main pid
-	if (!isDraft) {
+	// Normalize the path to allow for changes in upload_path (and so upload_url can be appended if needed)
+	if (relativePath) {
+		relativePath = relativePath.replace(nconf.get('upload_path'), '');
+	}
+
+	db.sortedSetAdd(set, numThumbs, value);
+
+	// Associate thumbnails with the main pid (only on local upload)
+	if (!isDraft && relativePath) {
 		const topics = require('.');
 		const mainPid = (await topics.getMainPids([id]))[0];
 		posts.uploads.associate(mainPid, relativePath.replace('/files/', ''));
@@ -59,7 +65,7 @@ Thumbs.migrate = async function (uuid, id) {
 	// Converts the draft thumb zset to the topic zset (combines thumbs if applicable)
 	const set = `draft:${uuid}:thumbs`;
 	const thumbs = await db.getSortedSetRange(set, 0, -1);
-	await Promise.all(thumbs.map(async path => await Thumbs.associate(id, path)));
+	await Promise.all(thumbs.map(async path => await Thumbs.associate({ id, path })));
 	await db.delete(set);
 };
 
diff --git a/test/topicThumbs.js b/test/topicThumbs.js
index 58574638fc..6d2d249801 100644
--- a/test/topicThumbs.js
+++ b/test/topicThumbs.js
@@ -13,6 +13,7 @@ const user = require('../src/user');
 const groups = require('../src/groups');
 const topics = require('../src/topics');
 const categories = require('../src/categories');
+const plugins = require('../src/plugins');
 const file = require('../src/file');
 const utils = require('../src/utils');
 
@@ -27,7 +28,7 @@ describe('Topic thumbs', () => {
 	let fooJar;
 	let fooCSRF;
 	let fooUid;
-	const thumbPaths = ['files/test.png', 'files/test2.png'];
+	const thumbPaths = ['files/test.png', 'files/test2.png', 'https://example.org'];
 	const uuid = utils.generateUUID();
 
 	function createFiles() {
@@ -106,18 +107,34 @@ describe('Topic thumbs', () => {
 
 	describe('.associate()', () => {
 		it('should add an uploaded file to a zset', async () => {
-			await topics.thumbs.associate(2, thumbPaths[0]);
+			await topics.thumbs.associate({
+				id: 2,
+				path: thumbPaths[0],
+			});
 
 			const exists = await db.isSortedSetMember(`topic:2:thumbs`, thumbPaths[0]);
 			assert(exists);
 		});
 
 		it('should also work with UUIDs', async () => {
-			await topics.thumbs.associate(uuid, thumbPaths[1]);
+			await topics.thumbs.associate({
+				id: uuid,
+				path: thumbPaths[1],
+			});
 
 			const exists = await db.isSortedSetMember(`draft:${uuid}:thumbs`, thumbPaths[1]);
 			assert(exists);
 		});
+
+		it('should also work with a URL', async () => {
+			await topics.thumbs.associate({
+				id: 2,
+				path: thumbPaths[2],
+			});
+
+			const exists = await db.isSortedSetMember(`topic:2:thumbs`, thumbPaths[2]);
+			assert(exists);
+		});
 	});
 
 	describe('.migrate()', () => {
@@ -125,13 +142,18 @@ describe('Topic thumbs', () => {
 			await topics.thumbs.migrate(uuid, 2);
 
 			const thumbs = await topics.thumbs.get(2);
-			assert.strictEqual(thumbs.length, 2);
+			assert.strictEqual(thumbs.length, 3);
 			assert.deepStrictEqual(thumbs, [
 				{
 					id: 2,
 					name: 'test.png',
 					url: `${nconf.get('upload_url')}/${thumbPaths[0]}`,
 				},
+				{
+					id: 2,
+					name: 'example.org',
+					url: 'https://example.org',
+				},
 				{
 					id: 2,
 					name: 'test2.png',
@@ -143,7 +165,10 @@ describe('Topic thumbs', () => {
 
 	describe(`.delete()`, () => {
 		it('should remove a file from sorted set AND disk', async () => {
-			await topics.thumbs.associate(1, thumbPaths[0]);
+			await topics.thumbs.associate({
+				id: 1,
+				path: thumbPaths[0],
+			});
 			await topics.thumbs.delete(1, thumbPaths[0]);
 
 			assert.strictEqual(await db.isSortedSetMember('topic:1:thumbs', thumbPaths[0]), false);
@@ -151,13 +176,26 @@ describe('Topic thumbs', () => {
 		});
 
 		it('should also work with UUIDs', async () => {
-			await topics.thumbs.associate(uuid, thumbPaths[1]);
+			await topics.thumbs.associate({
+				id: uuid,
+				path: thumbPaths[1],
+			});
 			await topics.thumbs.delete(uuid, thumbPaths[1]);
 
 			assert.strictEqual(await db.isSortedSetMember(`draft:${uuid}:thumbs`, thumbPaths[1]), false);
 			assert.strictEqual(await file.exists(`${nconf.get('upload_path')}/${thumbPaths[1]}`), false);
 		});
 
+		it('should also work with URLs', async () => {
+			await topics.thumbs.associate({
+				id: uuid,
+				path: thumbPaths[2],
+			});
+			await topics.thumbs.delete(uuid, thumbPaths[2]);
+
+			assert.strictEqual(await db.isSortedSetMember(`draft:${uuid}:thumbs`, thumbPaths[2]), false);
+		});
+
 		it('should not delete the file from disk if not associated with the tid', async () => {
 			createFiles();
 			await topics.thumbs.delete(uuid, thumbPaths[0]);
@@ -186,6 +224,27 @@ describe('Topic thumbs', () => {
 			});
 		});
 
+		it('should succeed with uploader plugins', async () => {
+			const hookMethod = async () => ({
+				name: 'test.png',
+				url: 'https://example.org',
+			});
+			await plugins.hooks.register('test', {
+				hook: 'filter:uploadFile',
+				method: hookMethod,
+			});
+
+			await new Promise((resolve) => {
+				helpers.uploadFile(`${nconf.get('url')}/api/v3/topics/${uuid}/thumbs`, path.join(__dirname, './files/test.png'), {}, adminJar, adminCSRF, function (err, res, body) {
+					assert.ifError(err);
+					assert.strictEqual(res.statusCode, 200);
+					resolve();
+				});
+			});
+
+			await plugins.hooks.unregister('test', 'filter:uploadFile', hookMethod);
+		});
+
 		it('should fail with a non-existant tid', (done) => {
 			helpers.uploadFile(`${nconf.get('url')}/api/v3/topics/2/thumbs`, path.join(__dirname, './files/test.png'), {}, adminJar, adminCSRF, function (err, res, body) {
 				assert.ifError(err);