Category: Blog

Mastering Linux Storage (Part 1): Diagnosing Disk Space & Decoding Partition Sector Geometry

As software engineers, our local development environments and Linux VMs are constantly under pressure. Docker images build up, dependencies proliferate, and build artifacts quietly consume system resources. Eventually, every developer faces that dreaded error message: No space left on device. When your disk fills up, the immediate instinct is to start deleting files or run […]
Denis Kraft 0 Comments

How to Fix Outlook SMTP Login Failed in Thunderbird

Fixing the “Login Failed” Error Recently, I set up Thunderbird as my email client and wanted to use it with my Outlook (Microsoft 365) mailbox. The initial setup was surprisingly smooth: I added my Outlook email address, entered my password, and within seconds, all my emails started landing in my Thunderbird inbox. Easy win — […]
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How to Upgrade Debian Bullseye to Bookworm

Debian released the new stable version 12 in June 2023. The codename this time is Bookworm, and this is the little green worm from Toy Story. If you run version 11 of Debian, you will have support roughly until June 2026. Those who don’t want to wait can follow this tutorial for the upgrade. Prerequisites […]
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Java Deserialization Attacks: Understanding and Preventing a Silent Killer

Most developers think of SQL injection, cross-site scripting, or authentication flaws when building secure Java applications. But lurking in the background is a critical, subtle and dangerous vulnerability: deserialization attacks. In fact, this class of issues is recognised by OWASP as part of the Top 10:2021 security risks, specifically under #8: Software and Data Integrity […]
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Understanding XXE Attacks in Java: A Hidden Risk in XML Processing

Security misconfiguration ranks as #5 in the OWASP Top 10 (2021) — and XML External Entity (XXE) vulnerabilities are a textbook example of this issue. While XML remains a foundational data format in many Java applications, improper configuration of XML parsers can expose serious security holes. XXE attacks are often overlooked but can lead to […]
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Path Traversal via File Upload in Java: What You Need to Know

File uploads are a common feature in many web applications, but they can be a serious security risk if not handled properly. One of the lesser-known (but highly dangerous) vulnerabilities is Path Traversal via File Upload. It’s a variation of an insecure file upload, which directly contributes to Broken Access Control, the #1 security risk […]
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SQL Injection in Java: Still a Threat — Here’s How to Stop It

In today’s connected world, data breaches are becoming alarmingly frequent, often caused by vulnerabilities in web applications. One of the most notorious and dangerous vulnerabilities is SQL Injection. In fact, Injection attacks (which include SQL Injection) are ranked #3 in the OWASP Top Ten 2021, highlighting how critical and widespread this problem remains—even after years of awareness. SQL Injection allows attackers […]
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CVE-2021-44228 Log4Shell Vulnerability in SAP Commerce Cloud on Premise

A lot of companies face the issue with the Log4Shell vulnerability at the moment. It is possible to exploit the log4j library Version Apache log4j <= 2.14.1 and run any (malicious) code from a remote machine. Unfortunately, there is still no official answer from SAP, therefore I want to share my knowledge on how to […]
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VirtualBox | Free Up Disk Space on Debian Guest

Do you know the feeling when a pop up comes up and reminds you to clean up your hard disk? Today, it happened to me and I checked the disk manager. I saw that my virtual machines use a lot of space. So I decided to clean them up and I want to show you […]
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Git Secret Tutorial

git-secret is a tool to encrypt files. It helps you to give another person access to this file and to remove the access again. So it helps to keep secrets confidential and share the secrets between authorized people. Without such a tool you would need to keep the secrets out of your version control system […]
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