openECSC 2025 Author Writeup

CTFTime event link: https://ctftime.org/event/2940

Writeup

• World Wide Web
  1. kv-messenger

Background

• Starts: 29 Sept. 2025, 18:00 UTC
• Ends: 05 Oct. 2025, 23:59 UTC

openECSC is a cybersecurity competition open to everyone that invites enthusiasts to participate without any kind of limitations. Launched in 2022 as an extension of the European Cybersecurity Challenge, it aims to broaden participation beyond traditional age and nationality restrictions, featuring a series of jeopardy-style CTF competition rounds. openECSC 2025 will run September 29th through October 5th

Categories:

• World Wide Web
• Cryptography
• Steganography
• Reverse Engineering
• Binary Exploitation
• Miscellaneous
• Computer Forensics

What you'll learned in this CTF

• World Wide Web
  1. kv-messenger - CSP bypass via a CRLF injection to response splitting CSP gadget and Transfer-Encoding trick in HTTP/1.1 to truncate invalid JavaScript syntax