diff --git a/.rubocop.yml b/.rubocop.yml
index b15522c..f8c0693 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -37,6 +37,15 @@ Metrics/MethodLength:
 Metrics/ClassLength:
   Enabled: false
 
+Metrics/BlockLength:
+  Enabled: false
+
+Layout/FirstHashElementIndentation:
+  Enabled: false
+
+Layout/FirstArrayElementIndentation:
+  Enabled: false
+
 Layout/EmptyLineAfterGuardClause:
   Enabled: false
 
diff --git a/index.erb b/index.erb
index c808ada..33febfe 100644
--- a/index.erb
+++ b/index.erb
@@ -8,6 +8,7 @@
       content="initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=no"
       />
     <meta name="signed_in" content="<%= @signed_in %>">
+    <meta name="csrf" content="<%= @csrf_token %>">
     <link rel="preconnect" href="https://fonts.googleapis.com" />
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
     <link
diff --git a/logman.rb b/logman.rb
index ee14a49..453aa80 100644
--- a/logman.rb
+++ b/logman.rb
@@ -2,10 +2,10 @@
 module Logman
   def self.log(log)
     file, line = caller(1, 1)[0].split(":")
-    File.write("log/main.log", "[#{Time.now}] {#{file}:#{line}} #{log}\n", mode: "a")
+    File.write("log/main.log", "[#{Time.now}] {#{file}:#{line}} #{log}\n", mode: "a") if ENV_HASH["ENV"] == "dev"
   end
 
   def self.imp(log)
-    File.write("log/imp.log", "[#{Time.now}] #{log}\n", mode: "a")
+    File.write("log/imp.log", "[#{Time.now}] #{log}\n", mode: "a") if ENV_HASH["ENV"] == "dev"
   end
 end
diff --git a/main.rb b/main.rb
index 9c59dd4..6db71b4 100644
--- a/main.rb
+++ b/main.rb
@@ -8,8 +8,6 @@ require "uri"
 require "xxhash"
 require "zlib"
 
-load "logman.rb"
-
 ALPHANUM = [*"0".."9", *"A".."Z", *"a".."z", "-", "_"].freeze
 
 env_data = File.exist?(".env") ? File.read(".env") : ""
@@ -20,10 +18,9 @@ env_data.each_line do |line|
   ENV_HASH[match[1]] = match[2]
 end
 
+load "logman.rb"
 # Logman.log ENV_HASH.inspect
 
-CODE_ENV = :dev
-
 db_file = File.expand_path("infinsweeper.db")
 DB = Sequel.connect("sqlite:///#{db_file}", single_threaded: false)
 DB.run("PRAGMA foreign_keys = ON;")
@@ -40,6 +37,8 @@ get "/" do
   @message = session.message || ""
   session.message = ""
   @signed_in = session.signed_in?.nil? ? false : true
+  @csrf_token = Array.new(32) { ALPHANUM.sample }.join
+  session["csrf_token"] = @csrf_token
   ERB.new(File.read("index.erb")).result(binding)
 end
 
@@ -53,23 +52,28 @@ post "/signup" do
   uid = session["user"]
   session.logout unless uid.nil? || $active_users[uid].nil?
   data = JSON.parse(request.body.read)
+  unless session.csrf_auth?
+    status 401
+    return { "message" => "Unauthorized (invalid CSRF token)!" }.to_json
+  end
+  session["csrf_token"] = Array.new(32) { ALPHANUM.sample }.join
   if data["email"].nil? || data["pass"].nil? || data["username"].nil?
     status 400
-    return { "message" => "Bad request made!" }.to_json
+    return { "message" => "Bad request made!", "csrf_token" => session["csrf_token"] }.to_json
   end
   signup_status = Players.mk_player(data["username"], data["email"], data["pass"])
   if signup_status[0] == 200
     login_status = session.login(data["username"], data["pass"])
     if login_status[0] == 200
       status 200
-      return { "message" => login_status[1], "success" => "true" }.to_json
+      return { "message" => login_status[1], "success" => "true", "csrf_token" => session["csrf_token"] }.to_json
     else
       status login_status[0]
-      return { "message" => login_status[1] }.to_json
+      return { "message" => login_status[1], "csrf_token" => session["csrf_token"] }.to_json
     end
   end
   status signup_status[0]
-  return { "message" => signup_status[1] }.to_json
+  return { "message" => signup_status[1], "csrf_token" => session["csrf_token"] }.to_json
 end
 
 get "/verify/:code" do
@@ -82,21 +86,30 @@ post "/login" do
   data = JSON.parse(request.body.read)
   session = Sessions.new request, response
   uid = session["user"]
+  Logman.log(request.env["HTTP_X_CSRF_TOKEN"].to_s + " " + session["csrf_token"].to_s)
+  unless session.csrf_auth?
+    status 401
+    return { "message" => "Unauthorized (invalid CSRF token)!" }.to_json
+  end
+  session["csrf_token"] = Array.new(32) { ALPHANUM.sample }.join
   if $active_users[uid] && !session.logout
     status 500
-    return { "message" => "Internal server error when signing the existing session out!" }.to_json
+    return {
+             "message" => "Internal server error when signing the existing session out!",
+             "csrf_token" => session["csrf_token"],
+           }.to_json
   end
   if data["username"].nil? || data["pass"].nil?
     status 400
-    return { "message" => "Bad request made!" }.to_json
+    return { "message" => "Bad request made!", "csrf_token" => session["csrf_token"] }.to_json
   end
   login_status = session.login(data["username"], data["pass"])
   if login_status[0] == 200
     status 200
-    return { "message" => login_status[1], "success" => "true" }.to_json
+    return { "message" => login_status[1], "success" => "true", "csrf_token" => session["csrf_token"] }.to_json
   else
     status login_status[0]
-    return { "message" => login_status[1] }.to_json
+    return { "message" => login_status[1], "csrf_token" => session["csrf_token"] }.to_json
   end
 end
 
diff --git a/players.rb b/players.rb
index cfc0e80..94222e0 100644
--- a/players.rb
+++ b/players.rb
@@ -9,21 +9,24 @@ module Players
   end
 
   def self.mk_player(username, email, pass)
-    raise ArgumentError, "Email format is wrong!" unless email.match?(/\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/)
+    # rubocop:disable Layout/LineLength
+    raise ArgumentError, "Email format is wrong!" unless
+      email.match?(%r[(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])])
+    # rubocop:enable Layout/LineLength
     raise ArgumentError, "Username must be at least 4 characters long and of valid format." unless
       username.match?(/\A[a-zA-Z][a-zA-Z0-9_.-]+\z/) && username.length >= 4
     raise ArgumentError, "Password must be at least 8 characters and of valid format." unless
       pass.match?(/\A[a-zA-Z0-9_.!?@#$%^&*()+=-]+\z/) && pass.length >= 8
 
     digest = XXhash.xxh32(pass, ENV_HASH["SALT"])
-    code = CODE_ENV == :prod ? Array.new(24) { ALPHANUM.sample }.join : "!"
+    code = ENV_HASH["ENV"] == "prod" ? Array.new(24) { ALPHANUM.sample }.join : "!"
 
     DB[
       "insert into Players (username, digest, email, activation_code) values (?, ?, ?, ?)",
       username, digest, email, code
     ].insert
 
-    send_email(:new, email, username, code) if CODE_ENV == :prod
+    send_email(:new, email, username, code) if ENV_HASH["ENV"] == "prod"
 
     [200, "Successfully signed up!"]
   rescue ArgumentError => e
diff --git a/public/src/js/accounts.js b/public/src/js/accounts.js
index e8c6a0f..ef40944 100644
--- a/public/src/js/accounts.js
+++ b/public/src/js/accounts.js
@@ -1,3 +1,5 @@
+const csrfMeta = document.querySelector('meta[name="csrf"]');
+var csrf = csrfMeta?.content;
 window.onload = async () => {
   const popup = document.getElementById("popup");
   const loginSection = document.getElementById("login");
@@ -71,11 +73,12 @@ window.onload = async () => {
     const { username, pass } = loginForm;
     const res = await fetch("/login", {
       method: "POST",
-      headers: { "Content-Type": "application/json" },
+      headers: { "Content-Type": "application/json", "X-CSRF-Token": csrf },
       body: JSON.stringify({ username: username.value, pass: pass.value }),
     });
     const data = await res.json();
     loginInfo.innerText = data.message;
+    csrf = data.csrf_token;
     if (data.success == "true") {
       loginButton.style.display = "none";
       signupButton.style.display = "none";
@@ -91,7 +94,7 @@ window.onload = async () => {
     const { username, email, pass } = signupForm;
     const res = await fetch("/signup", {
       method: "POST",
-      headers: { "Content-Type": "application/json" },
+      headers: { "Content-Type": "application/json", "X-CSRF-Token": csrf },
       body: JSON.stringify({
         username: username.value,
         email: email.value,
@@ -100,6 +103,7 @@ window.onload = async () => {
     });
     const data = await res.json();
     signupInfo.innerText = data.message;
+    csrf = data.csrf_token;
     if (data.success == "true") {
       loginButton.style.display = "none";
       signupButton.style.display = "none";
diff --git a/session.rb b/session.rb
index 34510c9..6489c36 100644
--- a/session.rb
+++ b/session.rb
@@ -40,17 +40,22 @@ class Sessions
     end
   end
 
+  # TODO: Use .all here
   def []=(key, val)
     session = @request.cookies["session"]
     session = session.nil? ? "{}" : Zlib::Inflate.inflate(Base64.decode64(session))
     session = JSON.parse(session)
     session[key] = val
+    Logman.log "Updated: #{key} to #{val}"
     compressed = Zlib::Deflate.deflate(JSON.generate(session))
     encoded = Base64.encode64(compressed)
     @response.set_cookie("session",
                          value: encoded,
                          path: "/",
-                         expires: Time.now + 360 * 24 * 60 * 60)
+                         expires: Time.now + 360 * 24 * 60 * 60,
+                         httponly: true,
+                         secure: ENV_HASH["ENV"] == "prod",
+                         samesite: :strict)
     uid = session["user"]
     DB["UPDATE SignedInUsers SET last_used_at = CURRENT_TIMESTAMP WHERE code = ?", uid].update if uid
   rescue JSON::ParserError, Zlib::Error
@@ -79,13 +84,19 @@ class Sessions
     @response.set_cookie("message",
                          value: val,
                          path: "/",
-                         expires: Time.now + 360 * 24 * 60 * 60)
+                         expires: Time.now + 360 * 24 * 60 * 60,
+                         secure: ENV_HASH["ENV"] == "prod",
+                         samesite: :strict)
   end
 
   def message
     @request.cookies["message"]
   end
 
+  def csrf_auth?
+    @request.env["HTTP_X_CSRF_TOKEN"] == self["csrf_token"]
+  end
+
   def all
     session = @request.cookies["session"]
     session = session.nil? ? "{}" : Zlib::Inflate.inflate(Base64.decode64(session))
@@ -107,7 +118,10 @@ class Sessions
     @response.set_cookie("session",
                          value: encoded,
                          path: "/",
-                         expires: Time.now + 360 * 24 * 60 * 60)
+                         expires: Time.now + 360 * 24 * 60 * 60,
+                         httponly: true,
+                         secure: ENV_HASH["ENV"] == "prod",
+                         samesite: :strict)
   rescue JSON::ParserError, Zlib::Error
     @response.delete_cookie("session")
   end