diff --git a/package.json b/package.json
index 3ffe1521a..8350269f4 100644
--- a/package.json
+++ b/package.json
@@ -20,17 +20,17 @@
     "devDependencies": {
         "@shelf/jest-mongodb": "^1.2.3",
         "@types/cross-spawn": "^6.0.2",
-        "@types/jest": "^26.0.19",
-        "@types/node": "^14.14.16",
+        "@types/jest": "^26.0.20",
+        "@types/node": "^14.14.20",
         "@types/semver": "^7.3.4",
         "@typescript-eslint/eslint-plugin": "^3.9.1",
         "@typescript-eslint/parser": "^3.9.1",
         "cross-spawn": "^7.0.3",
-        "eslint": "^7.16.0",
+        "eslint": "^7.17.0",
         "eslint-config-airbnb-base": "^14.2.1",
         "eslint-import-resolver-typescript": "^2.3.0",
         "eslint-plugin-import": "^2.22.1",
-        "globby": "^11.0.1",
+        "globby": "^11.0.2",
         "jest": "^26.6.3",
         "latest-version": "^5.1.0",
         "ora": "^5.2.0",
diff --git a/packages/hydrojudge/package.json b/packages/hydrojudge/package.json
index 2a9e0a734..288053eac 100644
--- a/packages/hydrojudge/package.json
+++ b/packages/hydrojudge/package.json
@@ -10,11 +10,11 @@
         "axios": "^0.21.1",
         "bson": "^4.2.2",
         "fs-extra": "^9.0.1",
-        "js-yaml": "^3.14.1",
+        "js-yaml": "^4.0.0",
         "lodash": "^4.17.20",
         "p-queue": "^6.6.1",
         "shell-quote": "^1.7.2",
-        "systeminformation": "^4.33.4",
+        "systeminformation": "^4.34.5",
         "yargs": "^16.2.0"
     },
     "peerDependencies": {
@@ -24,7 +24,7 @@
     "devDependencies": {
         "@types/bson": "^4.0.2",
         "@types/fs-extra": "^9.0.6",
-        "@types/js-yaml": "^3.12.5",
+        "@types/js-yaml": "^4.0.0",
         "@types/shell-quote": "^1.7.0"
     },
     "scripts": {
diff --git a/packages/hydrojudge/src/cases.ts b/packages/hydrojudge/src/cases.ts
index 8dc1d6f30..622767b2e 100644
--- a/packages/hydrojudge/src/cases.ts
+++ b/packages/hydrojudge/src/cases.ts
@@ -299,7 +299,7 @@ export default async function readCases(folder: string, cfg: Record<string, any>
     const yamlConfig = path.resolve(folder, 'config.yaml');
     let config;
     if (fs.existsSync(yamlConfig)) {
-        config = { ...yaml.safeLoad(fs.readFileSync(yamlConfig).toString()) as object, ...cfg };
+        config = { ...yaml.load(fs.readFileSync(yamlConfig).toString()) as object, ...cfg };
     } else if (fs.existsSync(iniConfig)) {
         config = { ...convertIniConfig(fs.readFileSync(iniConfig).toString()), ...cfg };
     } else config = cfg;
diff --git a/packages/hydrojudge/src/compile.ts b/packages/hydrojudge/src/compile.ts
index 9c07a019a..13823033e 100644
--- a/packages/hydrojudge/src/compile.ts
+++ b/packages/hydrojudge/src/compile.ts
@@ -9,7 +9,7 @@ export = async function compile(
     lang: string, code: string, target: string, copyIn: any, next?: Function,
 ): Promise<Execute> {
     const LANGS = global.Hydro
-        ? yaml.safeLoad(await global.Hydro.model.system.get('hydrojudge.langs'))
+        ? yaml.load(global.Hydro.model.system.get('hydrojudge.langs'))
         : require('./config').LANGS;
     if (!LANGS[lang]) throw new SystemError('Unsupported language {0}.', [lang]);
     const info = LANGS[lang];
diff --git a/packages/hydrojudge/src/config.ts b/packages/hydrojudge/src/config.ts
index 42c751a04..955358af4 100644
--- a/packages/hydrojudge/src/config.ts
+++ b/packages/hydrojudge/src/config.ts
@@ -47,12 +47,12 @@ if (process.env.EXECUTION_HOST || argv.execute) {
     EXECUTION_HOST = path.resolve(process.env.EXECUTION_HOST || argv.execute as string);
 }
 if (!global.Hydro) {
-    if (fs.existsSync(LANGS_FILE)) LANGS = yaml.safeLoad(fs.readFileSync(LANGS_FILE).toString());
+    if (fs.existsSync(LANGS_FILE)) LANGS = yaml.load(fs.readFileSync(LANGS_FILE).toString());
     else {
         log.error('Language file not found, using default.');
         const file = path.join(path.dirname(require.resolve('@hydrooj/hydrojudge')), 'setting.yaml');
-        const content = yaml.safeLoad(fs.readFileSync(file).toString()) as any;
-        LANGS = yaml.safeLoad(content.langs.default) as any;
+        const content = yaml.load(fs.readFileSync(file).toString()) as any;
+        LANGS = yaml.load(content.langs.default) as any;
     }
     if (!(fs.existsSync(LANGS_FILE) || global.Hydro)) {
         fs.ensureDirSync(path.dirname(LANGS_FILE));
diff --git a/packages/hydrojudge/src/daemon.ts b/packages/hydrojudge/src/daemon.ts
index 3af8f2b8c..e93d58fcf 100644
--- a/packages/hydrojudge/src/daemon.ts
+++ b/packages/hydrojudge/src/daemon.ts
@@ -57,7 +57,7 @@ async function daemon() {
         if (CONFIG) config = CONFIG;
         else {
             config = (await fs.readFile(CONFIG_FILE)).toString();
-            config = yaml.safeLoad(config);
+            config = yaml.load(config);
         }
     } catch (e) {
         log.error('配置文件无效或未找到。');
@@ -85,7 +85,7 @@ async function daemon() {
                 if (hosts[i].config.cookie) cfg.hosts[i].cookie = hosts[i].config.cookie;
                 if (hosts[i].config.detail) cfg.hosts[i].detail = hosts[i].config.detail;
             }
-            await fs.writeFile(CONFIG_FILE, yaml.safeDump(cfg));
+            await fs.writeFile(CONFIG_FILE, yaml.dump(cfg));
         });
     }
     while ('Orz twd2') {
diff --git a/packages/hydrooj/package.json b/packages/hydrooj/package.json
index 5acf8bd56..52549ed29 100644
--- a/packages/hydrooj/package.json
+++ b/packages/hydrooj/package.json
@@ -1,6 +1,6 @@
 {
     "name": "hydrooj",
-    "version": "2.15.15",
+    "version": "2.15.16",
     "bin": "bin/hydrooj.js",
     "main": "dist/loader.js",
     "typings": "dist/loader.d.ts",
@@ -16,8 +16,8 @@
         "cookies": "^0.8.0",
         "detect-browser": "^5.1.1",
         "fs-extra": "^9.0.1",
-        "js-yaml": "^3.14.1",
-        "koa": "^2.13.0",
+        "js-yaml": "^4.0.0",
+        "koa": "^2.13.1",
         "koa-body": "^4.2.0",
         "koa-proxies": "^0.11.0",
         "koa-router": "^10.0.0",
@@ -32,18 +32,18 @@
         "serialize-javascript": "^5.0.1",
         "sockjs": "^0.3.20",
         "superagent": "^6.1.0",
-        "systeminformation": "^4.33.4",
+        "systeminformation": "^4.34.5",
         "terminal-kit": "^1.44.3",
         "yargs": "^16.2.0"
     },
     "devDependencies": {
         "@types/adm-zip": "^0.4.33",
         "@types/fs-extra": "^9.0.6",
-        "@types/js-yaml": "^3.12.5",
+        "@types/js-yaml": "^4.0.0",
         "@types/koa": "^2.11.4",
         "@types/koa-router": "^7.4.1",
         "@types/koa-static-cache": "^5.1.0",
-        "@types/lodash": "^4.14.166",
+        "@types/lodash": "^4.14.167",
         "@types/lru-cache": "^5.1.0",
         "@types/minio": "^7.0.6",
         "@types/mongodb": "^3.5.33",
diff --git a/packages/hydrooj/src/entry/common.ts b/packages/hydrooj/src/entry/common.ts
index 8b6834c0c..c8b57a987 100644
--- a/packages/hydrooj/src/entry/common.ts
+++ b/packages/hydrooj/src/entry/common.ts
@@ -70,7 +70,7 @@ export async function locale(pending: string[], fail: string[]) {
                 const locales = {};
                 for (const file of files) {
                     const content = fs.readFileSync(path.resolve(p, file)).toString();
-                    locales[file.split('.')[0]] = yaml.safeLoad(content);
+                    locales[file.split('.')[0]] = yaml.load(content);
                 }
                 global.Hydro.lib.i18n(locales);
                 logger.info('Locale init: %s', i);
@@ -97,7 +97,7 @@ export async function setting(pending: string[], fail: string[], modelSetting: t
         if (!fs.existsSync(p)) p = path.resolve(i, 'settings.yaml');
         if (fs.existsSync(p) && !fail.includes(i)) {
             try {
-                const cfg: any = yaml.safeLoad(fs.readFileSync(p).toString());
+                const cfg: any = yaml.load(fs.readFileSync(p).toString());
                 for (const key in cfg) {
                     map[cfg[key].category || 'system'](
                         modelSetting.Setting(
diff --git a/packages/hydrooj/src/handler/homework.ts b/packages/hydrooj/src/handler/homework.ts
index 65a06f934..8b352042e 100644
--- a/packages/hydrooj/src/handler/homework.ts
+++ b/packages/hydrooj/src/handler/homework.ts
@@ -24,7 +24,7 @@ import paginate from '../lib/paginate';
 import { isTitle, isContent } from '../lib/validator';
 
 const validatePenaltyRules = (input: string) => {
-    const s = yaml.safeLoad(input);
+    const s = yaml.load(input);
     return s;
 };
 const convertPenaltyRules = validatePenaltyRules;
@@ -281,7 +281,7 @@ class HomeworkEditHandler extends HomeworkHandler {
             datePenaltyText: penaltySince.format('YYYY-M-D'),
             timePenaltyText: penaltySince.format('hh:mm'),
             extensionDays,
-            penaltyRules: yaml.safeDump(tdoc.penaltyRules),
+            penaltyRules: yaml.dump(tdoc.penaltyRules),
             pids: tdoc.pids.join(','),
             path,
         };
diff --git a/packages/hydrooj/src/handler/problem.ts b/packages/hydrooj/src/handler/problem.ts
index 35003bed4..0c009da38 100644
--- a/packages/hydrooj/src/handler/problem.ts
+++ b/packages/hydrooj/src/handler/problem.ts
@@ -363,7 +363,7 @@ export class ProblemSettingsHandler extends ProblemManageHandler {
             ['problem_settings', null],
         ];
         if (this.response.body.pdoc.config) {
-            this.response.body.pdoc.config = yaml.safeDump(this.response.body.pdoc.config);
+            this.response.body.pdoc.config = yaml.dump(this.response.body.pdoc.config);
         }
     }
 
@@ -372,7 +372,7 @@ export class ProblemSettingsHandler extends ProblemManageHandler {
     async postConfig(domainId: string, pid: string | number, cfg: string) {
         const pdoc = await problem.get(domainId, pid);
         // TODO validate
-        const config = yaml.safeLoad(cfg) as any;
+        const config = yaml.load(cfg) as any;
         await problem.edit(domainId, pdoc.docId, { config });
         this.back();
     }
diff --git a/packages/hydrooj/src/lib/testdata.convert.ini.ts b/packages/hydrooj/src/lib/testdata.convert.ini.ts
index 8a13249ee..976d19928 100644
--- a/packages/hydrooj/src/lib/testdata.convert.ini.ts
+++ b/packages/hydrooj/src/lib/testdata.convert.ini.ts
@@ -15,7 +15,7 @@ function convert(ini: string) {
         if (!Number.isNaN(parseInt(memory, 10))) cur.memory = `${Math.floor(parseInt(memory, 10) / 1024)}m`;
         res.subtasks.push(cur);
     }
-    return yaml.safeDump(res);
+    return yaml.dump(res);
 }
 
 global.Hydro.lib['testdata.convert.ini'] = convert;
diff --git a/packages/hydrooj/src/lib/testdataConfig.ts b/packages/hydrooj/src/lib/testdataConfig.ts
index 7046cd79f..f67442991 100644
--- a/packages/hydrooj/src/lib/testdataConfig.ts
+++ b/packages/hydrooj/src/lib/testdataConfig.ts
@@ -1,5 +1,5 @@
 import Zip from 'adm-zip';
-import { safeLoad } from 'js-yaml';
+import { load } from 'js-yaml';
 import { LocalProblemConfig } from '../interface';
 
 export async function readConfig(file: string | Buffer) {
@@ -37,7 +37,7 @@ export async function parseConfig(config: string | LocalProblemConfig) {
     let cfg: LocalProblemConfig = {};
     if (typeof config === 'string') {
         // TODO should validate here?
-        cfg = safeLoad(config) as LocalProblemConfig;
+        cfg = load(config) as LocalProblemConfig;
     } else cfg = config;
     if (cfg.cases) {
         for (const c of cfg.cases) {
diff --git a/packages/hydrooj/src/model/setting.ts b/packages/hydrooj/src/model/setting.ts
index 31022da8a..4bac005aa 100644
--- a/packages/hydrooj/src/model/setting.ts
+++ b/packages/hydrooj/src/model/setting.ts
@@ -1,6 +1,7 @@
 /* eslint-disable no-await-in-loop */
 import moment from 'moment-timezone';
 import { Dictionary } from 'lodash';
+import yaml from 'js-yaml';
 import * as builtin from './builtin';
 import { Setting as _Setting } from '../interface';
 import { Logger } from '../logger';
@@ -142,6 +143,7 @@ SystemSetting(
     Setting('setting_server', 'server.port', null, 8888, 'number', 'Server Port'),
     Setting('setting_server', 'server.xff', null, null, 'text', 'IP Header', 'e.g. x-forwarded-for (lowercase)'),
     Setting('setting_server', 'server.language', langRange, 'zh_CN', 'select', 'Default display language'),
+    Setting('setting_basic', 'problem.categories', null, yaml.dump(builtin.CATEGORIES), 'textarea', 'Problem Categories'),
     Setting('setting_session', 'session.keys', null, [String.random(32)], 'text', 'session.keys', null, FLAG_HIDDEN),
     Setting('setting_session', 'session.secure', null, false, 'boolean', 'session.secure'),
     Setting('setting_session', 'session.saved_expire_seconds', null, 3600 * 24 * 30, 'number', 'Saved session expire seconds'),
diff --git a/packages/hydrooj/src/service/monitor.ts b/packages/hydrooj/src/service/monitor.ts
index e12c20d54..f9d0c2803 100644
--- a/packages/hydrooj/src/service/monitor.ts
+++ b/packages/hydrooj/src/service/monitor.ts
@@ -1,7 +1,7 @@
 import cluster from 'cluster';
 import crypto from 'crypto';
 import axios from 'axios';
-import { safeDump } from 'js-yaml';
+import { dump } from 'js-yaml';
 import db from './db';
 import * as bus from './bus';
 import * as sysinfo from '../lib/sysinfo';
@@ -33,7 +33,7 @@ export async function feedback() {
         document.coll.find({ docType: document.TYPE_DISCUSSION }).count(),
         record.coll.find().count(),
     ]);
-    const payload = crypt(safeDump({
+    const payload = crypt(dump({
         _id: installid + mid.toString(),
         version,
         name,
diff --git a/packages/import-qduoj/handler.ts b/packages/import-qduoj/handler.ts
index 634d0cbe6..84ad293d4 100644
--- a/packages/import-qduoj/handler.ts
+++ b/packages/import-qduoj/handler.ts
@@ -98,7 +98,7 @@ class ImportQduojHandler extends Handler {
                 }
                 await storage.put(
                     `problem/${domainId}/${pid}/testdata/config.yaml`,
-                    Buffer.from(yaml.safeDump(config)),
+                    Buffer.from(yaml.dump(config)),
                 );
                 const data = await storage.list(`problem/${domainId}/${pid}/testdata/`, true);
                 await problem.edit(domainId, pid, { html: true, data });
diff --git a/packages/login-with-qq/package.json b/packages/login-with-qq/package.json
index a7550b10b..659a1114c 100644
--- a/packages/login-with-qq/package.json
+++ b/packages/login-with-qq/package.json
@@ -13,7 +13,7 @@
         "hydrooj": "^2.15.0"
     },
     "dependencies": {
-        "ws": "^7.4.1"
+        "ws": "^7.4.2"
     },
     "devDependencies": {
         "@types/ws": "^7.4.0"
diff --git a/packages/migrate-vijos/package.json b/packages/migrate-vijos/package.json
index 922067c64..ad4a40e39 100644
--- a/packages/migrate-vijos/package.json
+++ b/packages/migrate-vijos/package.json
@@ -10,14 +10,14 @@
         "build": "tsc"
     },
     "devDependencies": {
-        "@types/js-yaml": "^3.12.5",
+        "@types/js-yaml": "^4.0.0",
         "@types/mongodb": "^3.5.33"
     },
     "peerDependencies": {
         "hydrooj": "2.14.x"
     },
     "dependencies": {
-        "js-yaml": "^3.14.1",
+        "js-yaml": "^4.0.0",
         "mongodb": "^3.6.3"
     }
 }
\ No newline at end of file
diff --git a/packages/migrate-vijos/script.ts b/packages/migrate-vijos/script.ts
index 580a50476..1ce83f201 100644
--- a/packages/migrate-vijos/script.ts
+++ b/packages/migrate-vijos/script.ts
@@ -346,7 +346,7 @@ async function fix(doc) {
             w.on('error', reject);
             r.pipe(w);
         });
-        const config = yaml.safeLoad(await testdataConfig.readConfig(p));
+        const config = yaml.load(await testdataConfig.readConfig(p));
         await dst.collection('document').updateOne(
             { _id: doc._id },
             { $set: { config } },