Here you’ll find recommended Online-References, Cheatsheets and Books.

This collection is not complete and in no special order. It will get updated along my way, for sure.

References

OWASP
Exploit Database
Hacktricks
AppSecExplained
Markdownguide
PayloadsAllTheThings
CommandInjectionPayloadList
Hacking Study Guide
GTFOBins
The Odin Project

Cheatsheets

OWASP Cheatsheet
Markdown Cheatsheet
Can-I-take-over-xyz
Pentest Monkey Cheatsheets
Tib3rius SQL Injection Cheatsheet
0xdf Default 404 Pages

Books

M. Kofler et al.: Hacking und Security
Amberg/Schmid: Hacking Praxis-Guide
M. Kofler: Python Grundkurs
Clark/Downer: Red and Blue Team Field Manuals
Stuttard/Pinto: The Web Application Hacker's Handbook (oldie but goldie)

• Recommended
• References
• Cheatsheets
• Books