Introduction: The Illusion of Logging Out
Picture ceasing to hand in your office keycard only for it to still open up the building months down the line. That’s what this Facebook login session expiration bypass in Facebook Creator App is all about. Although users logged out from all devices or changed passwords, attackers could enjoy permanent access—uploading or delete posts, sending messages to followers ad infinitum. This was a Session persistence flaw, not a Session theft flaw, you’d have several functions which the App displayed a “Session Expired" but it actually turned a blind eye. The playing field was like this for businesses and for creators, the stakes were incredibly high, if one were to get hacked with either a compromised account it could be brand sabotage, or financial loss or you know reputation damage.
🔍 Case Study Breakdowns
Case Study1: Session Expiration Bypass in Facebook Creator App
The Never-Ending Session: How a Facebook Flaw Let Hackers Stay Logged In Forever
(And Why Logging Out Isn’t Always Enough)
| Vulnerability Type | Session expiration bypass via offline action queuing |
|---|
| Impact | Attackers could maintain permanent access to accounts—even after password changes or forced logouts. |
| Significance | This flaw turned a “log out all devices” feature into a placebo, undermining user trust in critical security controls. |
| Bounty Awarded | $2500 |
| Bug Bounty Writeup | Medium Article |
Vulnerability Explanation: When “Logged Out” Doesn’t Mean “Locked Out”
Imagine firing an employee, only to watch them keep working because their computer didn’t get the memo. That’s what happened here. Facebook Creator Studio—a tool for managing Pages—failed to fully invalidate sessions, allowing attackers to linger and tamper with sessions. ==Sessions are like temporary access badges: they should expire immediately when revoked. But in this case, the Facebook Creator App treated session termination as a suggestion, not a rule.==
Exploitation Process: Hacking in the Dark
Step 1: The “What If?” Moment
Ajay (the bounty hunter) thought to himself: “But what if logging out of your all sessions does not disable it in actuality?” His thought:Security features usually focuses on showing nice feedback on UI, but advantages consistency in backend.
Step 2: Two Devices, One Trap
- Device A (Laptop): Logged into Facebook Creator Studio.
- Device B (Phone): Also online.
- **Logout Triggeredilimn:From yAA Device A, he logouted all active sessions.
- Device B’s Response: Indicated “session expired” but….
Step 3: The Airplane Mode Trick
- Disable Wi-Fi/mobile data on device B.
- Restart app (still offline).
- Made a post, clicked “Publish button” (pu concurrently).
- Restored internet: The post uploaded to Facebook’s servers.
Creative Twist:
The application blindly trusted offline activities and failed to re-verify the session validity when it recabled. As if sending a package after your mailbox has been destroyed—the postal service still delivers it.
Mitigation
- Server-Side Session Kill Switches: Invalidate sessions globally, not just in the UI.
- Validate Before Syncronizing: Check session status before running through queus of actions.
- Force Reauthentication: Prompt login for high-risk actions following network indisposed.
**Pro Tip: Use Burp Suite to capture and replay requests post-logout. **
Stay skeptical, test offline, and remember: sessions can haunt you. 👻
Case Study 2: When a Typo Uncovers a Goldmine
Hacking Uber with a Single Slash: The XSS Trick That Stole Facebook Sessions
(And Why Tiny Flaws Can Have Massive Consequences)
| Vulnerability Type | Cross-Site Scripting (XSS) leading to Facebook session token theft |
|---|
| Impact | Full account takeover via stolen Facebook credentials. |
| Significance | A chain reaction of small flaws—bypassed filters, weak CSP, and misconfigured ACLs—turned a minor bug into a critical exploit. |
| Bounty Awarded | $1500 |
| Original Writeup | Medium Article |
Vulnerability Description: chained with Facebook’s API to steal tokens.
Picture the approach of a burglar prowling out from a broken window, and he finds that the keys for a vault are contained. That’s what happened here. One badly misconfigured Uber endpoint, coupled with poor security protection, enabled hackers to seize Facebook sessions—the reason, a missing slash and a case-sensitive oversight.
XSS is like putting a slug of flawed counterfeited in a mailbox: attackers vector bad scripts into materials finer websites, positive more than browsers to handle them. Here, Uber’s blog search endpoint (/es-CL/blog/santiago/search/) was also susceptible to user input sanitization issues.
Exploitation Process:
Step 1: The Midnight Hunt
Feeling stuck in bug hunt, the researcher pivoted to Uber at 2:00 AM. Brute-forcing endpoints is what led to a blog search page. His idea: “Static sites usually bury unused functionality”. Let’s poke it.”
Step 2: Breaking the Filter
Initial XSS payloads failed. But persistence paid off. Here is how the author came to this payload:
URL Encoder API let HTML tags to be passed like `<` and `>`, but forbid the `/` character and the word "script"; Encoding the slash as `%2f` and changing cases (e.g., `scripT`) to avoid those filters, the researcher managed to get around the algorithm. This allowed decrypting arbitrary JavaScript—to finally steal Facebook tokens which belonged to Uber user’s account.
- Bypass 1: Marianobit steeper %2f instead of / to avoid keyword blocking.
- Bypass 2: Use mixed-case
<scripT> to bypass case-sensitive filters.
Final Payload:
<%fscripT><script>confirm(document.domain)<%2fscripT>
This ran the Javascript wich prooved the vulnerability.
Step 3. Moving Up To Facebook Token Theft
At a hacker conference, a partner proposed the idea of binding the XSS to Facebook API. The point: *“Uber accepts Facebook IDs. If we can pull tokens, we own the account.” The last JavaScript used by the attacker is something like that:
The Kill Chain:
- Bait the victim to the malicious page carring the XSS.
- Run JavaScript to steal tokens by Facebook’s
FB.getLoginStatus().
- **Bypass CSP: Uber’s misconfigured content security policy trusted external scripts.
Creative Twist:
Uber’s login flow was split between www.uber.com (static site) and auth.uber.com (auth). XSS on the static site was still able to interact with logged in individuals - a big error.
Mitigation
Mitigation:
- Sanitize Input Unapologetically: Apply a broad galer of all html special-character unless admitted by explicitly.
- Köprü CSP:
script-src 'self' engelJosBu_scripts.
- Separate Authentication as Specific Cases: Dedicate login logic to be away from static-content.
How to Find Such Vulnerabilities in real world?
- **Fuzz Forgotten Page: Burp Suite o manualizzarsi.
- Break Filters Playfully: Entreprise encoding, case-swapping ou syntaxe cruelle.
- Think Outside The Box: Always ask yourself, “What can I link this vulnerability with?”
Case Study 3: Session - Jacking with clickjacking
Unmasking the Hidden Danger: How a Missing Header Led to Session Hijacking
(And What It Teaches Us About Web Security)
Introduction: The Silent Threat in Your Browser
| Vulnerability Type | Clickjacking via a missing X-FRAME-OPTIONS header |
|---|
| Impact | Attackers could steal session cookies, leading to full account takeover |
| Significance | This flaw bypassed the app’s otherwise robust defenses, proving that one weak link can break the chain. |
| Bounty Awarded | $100 |
| Original Writeup | Medium Article |
Click-JACKING: When Your Screen Lies to You
Clickjacking is akin to a magic trick of the web kind: attackers shield and conceals malicious elements on top of a genuine webpage, fooling victims into clicking something they really meant not to. Without the X-FRAME-OPTIONS header—which indicates whether a page can be framed—malsite can load text page in hidden iframe and hijack clicks.
Impact:
The weak endpoint disclosed the sensitive session data (usernames, session IDs) in its response. An attacker can engage in frame injection and trick a logged in user to perform activities (like click a hidden button) that expose session. Några exploit koden ingenting—bara vinande visuell bedrägeri.
Exploitation Process: The Art of Digital Sleuthing
Step 1: Finding Hidden Vectors
The researcher had put days into brute-forcing directories (i.e., checking each door in a building to discover the unlocked ones). The jackpot? An interfaz Endpoint (/ping/loggedIn) a la que se reciben los detalles sesión:
{"username": "arbazkiraak007", "sessionId": "54CA86A999CB2DE0CD87F1EB37289261-n3"}
Step 2: The “Aha!” Moment
Why check this endpoint for clickjack? Because it leaked session IDs. The defector’s thought process: “If I can frame this page, I can steal cookies secretly.” A quick sniff showed the absent X-FRAME-OPTIONS header—unlike other endpoints which framed undermined.
Step 3: The Copy-Paste Game
No advanced tools needed. He simply constructed a simple HTML page with the vulnerable endpoint embedded in an invisible iframe in it. When someone lands on malicious page and their browser quietly goes out and hits the target endpoint and shoots their session ID flying.
Creative Twist:
The endpoint itself was not interactive - it only leaked data. But by going through framing of it, so attacker can associate it with social engineer (i.e., “Click here for free gift!”, devious way to seduce users in generating the request.
Impact and Mitigation: When a Small Flaw Becomes a Big Problem
Worst-Case Scenario: Account takeover, data breaches, or lateral movement within the app.
Mitigation:
- Add the Header: Set
X-FRAME-OPTIONS: DENY or SAMEORIGIN on all endpoints.
- Content Security Policy (CSP): Use
frame-ancestors to whitelist trusted domains.
- Audit Relentlessly: Automated scans miss edge cases. Manually review lesser-used endpoints.
Conclusion: Trust, But Verify
Any security system’s vulnerability stems from its weakest point since the Facebook Creator App displayed such a weakness. The implementation of bypasses in security systems occurs when developers choose to enable user-friendly features instead of fundamental security provisions.
The Facebook Creator App vulnerability points to multiple vital lessons we need to learn from it.
Visual logout confirmation deceives users because it does not terminate server-based sessions effectively.
Security integrity requires that offline operational features must make users re-authenticate upon re-connecting to network services.
Every feature needs to pass complete tests within different connection setups which test for system weaknesses during unstable wireless network situations.
Security professionals need to implement more than code review services because they should adopt zettachrisity which requires server-sided verification before granting session access. Electronic hackers persistently exploit these vulnerability gaps by targeting the offline queue systems because they contain greater accessibility weaknesses than complex secure systems.
Stay skeptical, test offline, and remember: sessions can haunt you. 👻
