The short version: Your login page is the busiest door in your game, and on launch day it's the one attackers try first. The flaws that hand over player accounts are rarely exotic. They're in how accounts link, who the server lets see what, and how sessions and resets are handled. Here are the five we find most, and how to close them before your players pay for it.
Why Account Takeover Peaks on Launch Day
Over the last few weeks, we've looked at what launch day does to your servers and what happens to your economy when a game goes online. This final part is about the thing that ties both together: your players' accounts.
On launch day, your login page takes more traffic than any other part of your game. Every player passes through it. That makes it the busiest door you own, and the one attackers try first.
It's also where staggered launches quietly add risk. When online arrives months after the story, players who have been playing alone suddenly need to link platform accounts, carry progress across and sign in to new services. That's a lot of new authentication logic, shipped all at once, on the busiest day of the year.
An account is worth far more than a login. It holds purchases, progress, rare items, payment details and personal data. When one is taken over, the player doesn't blame the attacker. They blame your game.
So rather than another list of best practice, I want to show you what we actually find when we test account systems before launch.
How to Read This Account Security Report
What follows is written the way we'd write up a real engagement. Each finding is a pattern that comes up again and again across online launches. Under each one, you'll find a real example from our published, anonymised report templates, with the CVSS score we gave it.
Each finding has a typical severity, from Medium to Critical, based on how much damage it usually does and how easy it is to exploit. The real examples carry their exact CVSS scores, the industry standard scale we use in every report. Then you get what we find, why it matters and how to fix it.
If you recognise your own systems in any of them, that's the point.
Finding 01: Broken Access Control (IDOR) on Player Accounts
Severity: High to Critical
What we find. A player requests their own inventory, profile or purchase history. The request includes an account ID. Change that ID, and the server returns someone else's data, or lets you act on their account. The login was secure. What happened after it wasn't.
From a real report. Our anonymised web report includes three versions of this. Changing the from and to fields on a transfer request let one user move another user's balance (Critical, CVSS 9.1). Swapping in another player's userId let them pay fees out of someone else's account (High, 8.2). And removing a single parameter from a notifications request returned every user's notifications (High, 7.5).
Why it matters. It's one of the most common serious findings in any backend, and games are no exception. Depending on the endpoint, it can expose personal data, leak purchase history or let one player spend, gift or delete another player's items. For a CISO, it's also a data protection incident waiting to happen.
The fix. Check ownership on every single request, server side, against the authenticated session rather than an ID the client sends. Test it endpoint by endpoint, because one forgotten route is enough.
Finding 02: Insecure Account Linking and Cross-Platform Sign In
Severity: Critical
What we find. Most online games let players sign in through a console or PC platform, then link that identity to the studio's own account system. The linking step is where things go wrong. The backend accepts a platform identity without fully verifying it, or links an account without proving the player owns both sides. The result: one player's platform login ends up attached to someone else's profile.
From a real report. In one of our published, anonymised desktop reports, the game server took the userId a player sent at login rather than deriving it from their authenticated platform account. Rated High (CVSS 7.5), it let an attacker break entire matches. In an account linking flow, the same mistake of trusting the identity the client claims is how one player ends up inside another's profile.
Why it matters. This is a full takeover, with no password needed. Progress, purchases and inventory all move to the attacker. And because linking usually ships alongside cross-platform play and cross-progression, it tends to arrive late, under deadline pressure.
The fix. Verify every platform token server side with the platform itself, never on the client's say so. Require proof of ownership for both accounts before linking, and treat unlinking and relinking as sensitive actions with their own checks.
Finding 03: Password Reset and Account Recovery Vulnerabilities
Severity: High
What we find. Studios put real effort into the front door, then leave the back door unlocked. Reset tokens that can be guessed or reused, reset links that never expire, recovery flows that leak whether an email has an account, or support processes that hand over accounts on thin evidence.
From a real report. In our anonymised web report, the password recovery endpoint confirmed whether an email address had an account (Medium, CVSS 5.3). On its own, that hands an attacker a list of valid targets. Paired with Finding 05, it's the first step of a takeover campaign.
Why it matters. An attacker doesn't need a player's password if they can reset it. And because recovery flows are used less often, they're tested less often, so flaws can sit there for years.
The fix. Make reset tokens long, random, single use and short lived. Invalidate all existing sessions when a password changes. Give the same response whether or not an account exists. And treat your support team's recovery process as part of your attack surface, because attackers certainly do.
Finding 04: Session Hijacking and Token Replay
Severity: Medium to High
What we find. Session tokens that never expire, survive a password change or logout, or can be captured and replayed from another device. Game clients are especially prone to this, because studios want players to stay signed in without friction, so tokens are made long lived and rarely checked again.
From a real report. Across our anonymised reports, sessions turn up in the wrong places again and again: tokens that stayed valid after logout on both web and mobile (Medium, CVSS 4.4 and 4.5), a game launcher writing session tokens into its logs (High, 7.9), the same launcher handing a session token to anyone on the local network (High, 7.1), and an auth token sent unencrypted over game traffic (Medium, 6.8).
Why it matters. A stolen token is a stolen account, often with no password, alert or second factor in the way. And if logging out or changing a password doesn't kill old sessions, a player who knows they've been compromised can't actually lock the attacker out.
The fix. Keep access tokens short lived and refresh them securely. Bind sessions to the device or context they were issued for. Make logout, password changes and suspicious activity revoke every active session, not just the current one.
Finding 05: Credential Stuffing When Login Protections Are Relaxed
Severity: High
What we find. In Part One, we warned that rate limits can mistake a genuine launch crowd for an attack. Some teams solve that by loosening limits and lockouts for launch week. That keeps legitimate players flowing. It also leaves the login wide open to automated password guessing and credential stuffing, hidden inside traffic that already looks enormous.
From a real report. Our anonymised web report shows how quietly protections can fail. The site sent a reCAPTCHA response with every request, but the server never checked it. It looked protected and wasn't. The report logs it as informational, because nothing breaks on its own, but in a credential stuffing attack it's the difference between a wall and a painted door.
Why it matters. Credential stuffing works because players reuse passwords from other breached services. On a normal day, unusual login volume stands out. On launch day, it's camouflaged. By the time anyone notices, a share of the accounts created or used that week may already be compromised.
The fix. Don't choose between availability and protection. Test both together, under real launch load, so you can set limits that let genuine crowds through and still catch automation. Add bot detection, offer two factor authentication, and watch for login patterns rather than raw volume.
The Business Cost of Account Takeover for Game Studios
An exploit damages your economy. An account takeover damages your relationship with a specific, real person who trusted you with their time, money and data.
For a CISO, account systems are where game security meets regulation. Personal data, payment details and purchase histories all sit behind that login. A takeover at scale isn't just a player support problem. It can become a reportable data protection incident.
For a studio head, the cost shows up everywhere at once: support queues full of locked out players, refunds and chargebacks, restored items you have to rebuild by hand, and players who simply don't come back. And just like outages and exploits, takeovers get posted. "Lost my account on day one" is a headline no studio wants trending.
The common thread across all five findings is that none of them are visible from the outside until someone exploits them. They have to be tested for.
Trusted by Game Studios
"After a year of collaborating with Cyrex on multiple game security assessments, their team has been instrumental in helping us identify and address security concerns." Amazon Games
Account Security Testing Before Your Next Launch
Every finding in this post came from testing account systems the way an attacker would, not by reviewing a checklist.
Want to see what that looks like in full? Our anonymised report templates show real findings, CVSS scoring and recommended fixes from desktop, mobile and web game engagements.
Our penetration testing engagements run on pair hacking: a senior offensive engineer working alongside Deus Rex, our autonomous AI pentesting agent. Deus Rex maps every endpoint and works through them at scale, which is exactly what catches the one forgotten route in Finding 01. The engineer chains what it finds into real takeover paths.
For the traffic between your game and its account services, we use Cyrex Protoceptor to intercept, replay and forge it, testing token replay, session hijacking and authentication bypass directly.
And because Finding 05 only shows up under real launch conditions, we can put your login under real launch load with Cyrex Swarm while our security engineers check your protections still hold, so you don't have to choose between keeping players in and keeping attackers out.
Response within 24 hours. NDA included. No commitment required.
Launch Season Recap: Servers, Economies and Accounts
That's the end of our Launch Season series. Three parts, three very different problems.
Part One was about servers: launch traffic arrives as a wall, and the first minutes decide how you're remembered. Part Two was about economies: the moment a game goes online, a slice of your players start playing your systems instead. And this part was about accounts: the busiest door in your game, and the one attackers try first.
The lesson underneath all three is the same: every one of these problems is cheaper to find in a test than in public.
Servers, economies, accounts. Test all three before your players do.
Written by Mathieu Huysman
Mathieu is Co-Founder and CCO of Cyrex, the driving force behind the company's commercial growth since day one, with 11+ years of hands-on expertise across application security, penetration testing, and multiplayer architecture. He brings rare technical depth to every client conversation - because at Cyrex, expertise isn't just what's sold, it's what's lived.
