diff --git a/.changeset/fast-ligers-unite.md b/.changeset/fast-ligers-unite.md
new file mode 100644
index 0000000000000..eacb88108a0f7
--- /dev/null
+++ b/.changeset/fast-ligers-unite.md
@@ -0,0 +1,5 @@
+---
+'@rocket.chat/meteor': patch
+---
+
+Security Hotfix (https://docs.rocket.chat/docs/security-fixes-and-updates)
diff --git a/apps/meteor/app/api/server/lib/isValidQuery.ts b/apps/meteor/app/api/server/lib/isValidQuery.ts
index b4dd70c2ae0d6..97620cdb1b9ef 100644
--- a/apps/meteor/app/api/server/lib/isValidQuery.ts
+++ b/apps/meteor/app/api/server/lib/isValidQuery.ts
@@ -23,16 +23,22 @@ export const isValidQuery: {
 const verifyQuery = (query: Query, allowedAttributes: string[], allowedOperations: string[], parent = ''): boolean => {
 	return Object.entries(removeDangerousProps(query)).every(([key, value]) => {
 		const path = parent ? `${parent}.${key}` : key;
-		if (parent === '' && path.startsWith('$')) {
-			if (!allowedOperations.includes(path)) {
-				isValidQuery.errors.push(`Invalid operation: ${path}`);
+		if (key.startsWith('$')) {
+			if (!allowedOperations.includes(key)) {
+				isValidQuery.errors.push(`Invalid operation: ${key}`);
 				return false;
 			}
-			if (!Array.isArray(value)) {
-				isValidQuery.errors.push(`Invalid parameter for operation: ${path} : ${value}`);
-				return false;
+
+			if (Array.isArray(value)) {
+				return value.every((v) => verifyQuery(v, allowedAttributes, allowedOperations));
 			}
-			return value.every((v) => verifyQuery(v, allowedAttributes, allowedOperations));
+
+			if (value instanceof Object) {
+				return verifyQuery(value, allowedAttributes, allowedOperations, path);
+			}
+
+			// handles primitive values (strings, numbers, booleans, etc.)
+			return true;
 		}
 
 		if (
diff --git a/apps/meteor/app/api/server/v1/users.ts b/apps/meteor/app/api/server/v1/users.ts
index d4f0012cd5784..f6058085deeec 100644
--- a/apps/meteor/app/api/server/v1/users.ts
+++ b/apps/meteor/app/api/server/v1/users.ts
@@ -50,7 +50,7 @@ import {
 } from '../../../lib/server/functions/checkUsernameAvailability';
 import { deleteUser } from '../../../lib/server/functions/deleteUser';
 import { getAvatarSuggestionForUser } from '../../../lib/server/functions/getAvatarSuggestionForUser';
-import { getFullUserDataByIdOrUsernameOrImportId } from '../../../lib/server/functions/getFullUserData';
+import { getFullUserDataByIdOrUsernameOrImportId, defaultFields, fullFields } from '../../../lib/server/functions/getFullUserData';
 import { generateUsernameSuggestion } from '../../../lib/server/functions/getUsernameSuggestion';
 import { saveCustomFields } from '../../../lib/server/functions/saveCustomFields';
 import { saveCustomFieldsWithoutValidation } from '../../../lib/server/functions/saveCustomFieldsWithoutValidation';
@@ -503,13 +503,18 @@ API.v1.addRoute(
 			const { offset, count } = await getPaginationItems(this.queryParams);
 			const { sort, fields, query } = await this.parseJsonQuery();
 
-			const nonEmptyQuery = getNonEmptyQuery(query, await hasPermissionAsync(this.userId, 'view-full-other-user-info'));
 			const nonEmptyFields = getNonEmptyFields(fields);
 
 			const inclusiveFields = getInclusiveFields(nonEmptyFields);
 
 			const inclusiveFieldsKeys = Object.keys(inclusiveFields);
 
+			const hasUserQuery = query && Object.keys(query).length > 0;
+
+			const nonEmptyQuery = getNonEmptyQuery(query, await hasPermissionAsync(this.userId, 'view-full-other-user-info'));
+
+			// if user provided a query, validate it with their allowed operators
+			// otherwise we use the default query (with $regex and $options)
 			if (
 				!isValidQuery(
 					nonEmptyQuery,
@@ -521,7 +526,7 @@ API.v1.addRoute(
 						inclusiveFieldsKeys.includes('type') && 'type.*',
 						inclusiveFieldsKeys.includes('customFields') && 'customFields.*',
 					].filter(Boolean) as string[],
-					this.queryOperations,
+					hasUserQuery ? this.queryOperations : [...this.queryOperations, '$regex', '$options'],
 				)
 			) {
 				throw new Meteor.Error('error-invalid-query', isValidQuery.errors.join('\n'));
@@ -1144,8 +1149,13 @@ API.v1.addRoute(
 			const selector: { exceptions: Required<IUser>['username'][]; conditions: Filter<IUser>; term: string } = JSON.parse(selectorRaw);
 
 			try {
-				if (selector?.conditions && !isValidQuery(selector.conditions, ['*'], ['$or', '$and'])) {
-					throw new Error('error-invalid-query');
+				if (selector?.conditions) {
+					const canViewFullInfo = await hasPermissionAsync(this.userId, 'view-full-other-user-info');
+					const allowedFields = canViewFullInfo ? [...Object.keys(defaultFields), ...Object.keys(fullFields)] : Object.keys(defaultFields);
+
+					if (!isValidQuery(selector.conditions, allowedFields, ['$and', '$ne', '$exists'])) {
+						throw new Error('error-invalid-query');
+					}
 				}
 			} catch (e) {
 				return API.v1.failure(e);
diff --git a/apps/meteor/app/lib/server/functions/getFullUserData.ts b/apps/meteor/app/lib/server/functions/getFullUserData.ts
index f66f8ecb49c66..c55a5464a2a8b 100644
--- a/apps/meteor/app/lib/server/functions/getFullUserData.ts
+++ b/apps/meteor/app/lib/server/functions/getFullUserData.ts
@@ -7,7 +7,7 @@ import { settings } from '../../../settings/server';
 
 const logger = new Logger('getFullUserData');
 
-const defaultFields = {
+export const defaultFields = {
 	name: 1,
 	username: 1,
 	nickname: 1,
@@ -24,7 +24,7 @@ const defaultFields = {
 	statusLivechat: 1,
 } as const;
 
-const fullFields = {
+export const fullFields = {
 	emails: 1,
 	phone: 1,
 	statusConnection: 1,
diff --git a/apps/meteor/tests/unit/app/api/server/v1/lib/isValidQuery.spec.ts b/apps/meteor/tests/unit/app/api/server/v1/lib/isValidQuery.spec.ts
index e67ad244066f2..5f421578ed480 100644
--- a/apps/meteor/tests/unit/app/api/server/v1/lib/isValidQuery.spec.ts
+++ b/apps/meteor/tests/unit/app/api/server/v1/lib/isValidQuery.spec.ts
@@ -174,7 +174,7 @@ describe('isValidQuery', () => {
 					},
 				},
 			};
-			expect(isValidQuery(query, props, ['$or'])).to.be.true;
+			expect(isValidQuery(query, props, ['$or', '$regex'])).to.be.true;
 			expect(isValidQuery.errors.length).to.be.equals(0);
 		});
 
@@ -212,5 +212,15 @@ describe('isValidQuery', () => {
 				),
 			).to.be.false;
 		});
+
+		it('should return false if the query contains nested conditions with disallowed operators', () => {
+			const props = ['username'];
+			const allowedOps = ['$and', '$ne'];
+			const query = {
+				$and: [{ username: { $exists: true } }, { username: { $ne: '1000' } }],
+			};
+			expect(isValidQuery(query, props, allowedOps)).to.be.false;
+			expect(isValidQuery.errors.length).to.be.equals(1);
+		});
 	});
 });