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Posts by pspaul

From intent extra to RCE: Argument injection in YTDLnis Discover a vulnerability our researchers found in the Android app YTDLnis, allowing attackers to execute code on victim devices.

📱 1-click RCE in the YTDLnis Android app!

On Android, turning file writes into RCE is usually quite hard, but here the app had a nice gadget for us. Check out the details in our latest blog post:

www.sonarsource.com/blog/ytdlnis...

#appsec #security #vulnerability

4 weeks ago 2 1 0 0

🧟 A fixed vulnerability that comes back to life?

This could have happened in GitHub Actions until yesterday! Learn how attackers could have exploited seemingly fixed workflow vulnerabilities:

www.sonarsource.com/blog/zombie-...

#appsec #security #vulnerability

4 months ago 2 1 0 0
TROOPERS25: Scriptless Attacks - Why CSS is My Favorite Programming Language
TROOPERS25: Scriptless Attacks - Why CSS is My Favorite Programming Language YouTube video by TROOPERS IT Security Conference

My TROOPERS25 talk has been uploaded! If you ever wondered if "style-src: 'unsafe-line'" in your CSP is bad, this one is for you.

Scriptless Attacks: Why CSS is My Favorite Programming Language
www.youtube.com/watch?v=Owp-...

4 months ago 0 0 0 0

This was pretty fun to exploit! Even though I didn't manage to pwn the version used for Pwn2Own Berlin, I still learned a ton about LLMs. Maybe I can get my revenge in future competitions 🤞

5 months ago 5 1 0 0

Using SonarQube to solve a CTF challenge? Done! ✅

Learn how we detected a 0-day vulnerability during #KalmarCTF, making us first to solve the challenge! From Zip Slip to RCE, using lazy class loading:

www.sonarsource.com/blog/code-se...

#appsec #CTF #vulnerability

7 months ago 3 1 0 0
Caught in the FortiNet: How Attackers Can Exploit FortiClient to Compromise Organizations (3/3) In the last blog of this series, we will focus back on FortiClient and learn how the inner workings of this application work, and what crucial mistake happened that led to us uncovering a local privil...

🔓⏫ After compromising every endpoint within an organization, our “Caught in the FortiNet” blog series comes to an end with one more thing.
Read more about FortiClient's XPC mistake that allows local privilege escalation to root on macOS:

www.sonarsource.com/blog/caught-...

#appsec #security

9 months ago 3 2 0 0
Caught in the FortiNet: How Attackers Can Exploit FortiClient to Compromise Organizations (2/3) We recently discovered critical vulnerabilities in Fortinet’s endpoint protection solution that enable attackers to fully compromise organizations with minimal user interaction. In this second article...

📁🫷🚧Can't control the extension of a file upload, but you want an XSS?
Read more on how we overcame this obstacle to further exploit entire organizations using Fortinet endpoint protection:

www.sonarsource.com/blog/caught-...

#appsec #vulnerability #bugbountytips

9 months ago 1 1 0 0

Great bug chain by my team mate Yaniv that can pwn a whole org, starting with a single user click! I was also able to contribute a bit by creating my first port of a Chrome n-day exploit :)

9 months ago 0 0 0 0
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Catch our second talk at #TROOPERS25:

🕸️ Caught in the FortiNet: Compromising Organizations Using Endpoint Protection

Yaniv Nizry will tell you the story of multiple vulnerabilities in Fortinet products that can compromise an entire organization, starting with a single click

9 months ago 4 1 0 0
Title: Scriptless Attacks: Why CSS is My Favorite Programming Language
Speaker: Paul Gerste, Vulnerability Researcher, Sonar
Date: Wednesday, June 25, 2025
Time: 2:15 pm
Location: Track 3

Title: Scriptless Attacks: Why CSS is My Favorite Programming Language Speaker: Paul Gerste, Vulnerability Researcher, Sonar Date: Wednesday, June 25, 2025 Time: 2:15 pm Location: Track 3

Coming to #TROOPERS25 this week? We'll be there too, presenting our research!

🎨 Scriptless Attacks: Why CSS is My Favorite Programming Language

@pspaul95.bsky.social will convince you why CSS should not be overlooked in client-side web attacks and what is possible without JavaScript today

9 months ago 4 2 0 0

This was a fun one to discover!
SQL syntax can be ambiguous, and MySQL anticipated this a long time ago. Other SQL dialects stuck to the spec, leading to SQL injection when the right stars align:

10 months ago 1 0 0 0

my dream browser vuln is one entirely exploitable from CSS, no JS involved. not sure how feasible that really is tho, even with all the modern conditional CSS tricks

11 months ago 2 0 1 0
Data in Danger: Detecting Cross-Site Scripting in Grafana Learn how SonarQube detected a Cross-Site Scripting (XSS) vulnerability in Grafana, a popular open-source data observability platform.

📊⚠️ Data in danger!

We found an XSS vulnerability in Grafana with the help of SonarQube. Learn about the details in our latest blog post:

www.sonarsource.com/blog/data-in...

#appsec #security #vulnerability

11 months ago 3 2 0 0
Browser compatibility
There is no browser implementing this feature.

Browser compatibility There is no browser implementing this feature.

"wow, this css property would be amazing for my css crime, i wonder what the browser support is looking like"

1 year ago 42 4 1 0
Preview
GymTok: Breaking TLS Using the Alt-Svc Header Ever wondered what the Alt-Svc response header is used for? Turns out it can be used to become a Man-in-the-Middle and attack TLS!

Ever wondered what the Alt-Svc header is used for? Well, it can make you a MitM if you control it!

I can finally publish the writeup to my GymTok challenge: control the header, become MitM, and perform a cross-protocol attack!

blog.pspaul.de/posts/gymtok...

1 year ago 2 2 0 0

Wow, thanks for 2nd place! Didn't expect this, maybe it's my sign to finally write it down in text form and tackle all the follow-up ideas 👀

1 year ago 8 1 1 0