diff --git a/src/topics/sorted.js b/src/topics/sorted.js
index c2f916718e..98292f0ddb 100644
--- a/src/topics/sorted.js
+++ b/src/topics/sorted.js
@@ -45,7 +45,7 @@ module.exports = function (Topics) {
 		let tids = [];
 		if (params.term !== 'alltime') {
 			if (params.sort === 'posts') {
-				tids = await getTidsWithMostPostsInTerm(params.term);
+				tids = await getTidsWithMostPostsInTerm(params.cids, params.uid, params.term);
 			} else {
 				tids = await Topics.getLatestTidsFromSet('topics:tid', 0, -1, params.term);
 			}
@@ -84,8 +84,20 @@ module.exports = function (Topics) {
 		return 'topics:recent';
 	}
 
-	async function getTidsWithMostPostsInTerm(term) {
-		const pids = await db.getSortedSetRevRangeByScore('posts:pid', 0, 1000, '+inf', Date.now() - Topics.getSinceFromTerm(term));
+	async function getTidsWithMostPostsInTerm(cids, uid, term) {
+		if (Array.isArray(cids)) {
+			cids = await privileges.categories.filterCids('topics:read', cids, uid);
+		} else {
+			cids = await categories.getCidsByPrivilege('categories:cid', uid, 'topics:read');
+		}
+
+		const pids = await db.getSortedSetRevRangeByScore(
+			cids.map(cid => `cid:${cid}:pids`),
+			0,
+			1000,
+			'+inf',
+			Date.now() - Topics.getSinceFromTerm(term)
+		);
 		const postObjs = await db.getObjectsFields(pids.map(pid => `post:${pid}`), ['tid']);
 		const tidToCount = {};
 		postObjs.forEach((post) => {
@@ -93,7 +105,8 @@ module.exports = function (Topics) {
 			tidToCount[post.tid] += 1;
 		});
 
-		return _.uniq(postObjs.map(post => String(post.tid))).sort((t1, t2) => tidToCount[t2] - tidToCount[t1]);
+		return _.uniq(postObjs.map(post => String(post.tid)))
+			.sort((t1, t2) => tidToCount[t2] - tidToCount[t1]);
 	}
 
 	async function getWatchedTopics(params) {