50 past challenges
What does this program print?
Given the class union below, what does the TypeScript compiler do with animal.bark() and animal.meow()?
What does this code log to the console?
A Job is created with the pod template below, which sets restartPolicy: Always. What happens when you apply it?
On a switched Ethernet LAN, an attacker on the same subnet repeatedly sends unsolicited ARP replies mapping the default gateway's IP to the attacker's own MAC address. Victim hosts update their ARP caches and start sending gateway-bound traffic to the attacker, who forwards it. What makes this attack possible?
What does this Go program print?
What is the resolved type of `x` below?
What does this code log to the console?
A container sets securityContext.readOnlyRootFilesystem: true, as shown. Its process needs to write temporary files to /tmp. What is the effect of this setting, and what must you add for the writes to succeed?
This C function is compiled with GCC's -fstack-protector-strong, and an attacker overflows buf via the unchecked strcpy. How does the inserted stack canary defend against the classic 'overwrite the saved return address' exploit?
What does this Go program print?
Using the `Record` utility type below, what is the resolved type of `Config`?
What does this code log?
You run `kubectl rollout restart deployment/web`. The Deployment's image and configuration are otherwise unchanged. What does this command do?
This Node.js endpoint fetches any URL the client supplies and returns the body. An attacker submits `http://169.254.169.254/latest/meta-data/iam/security-credentials/web-role`. On AWS, why is this SSRF target especially dangerous, and what mitigates it?
What does this Go program print?
With `x` typed as `unknown`, which single operation does the compiler allow without any narrowing?
What does this code log?
A Deployment sets spec.revisionHistoryLimit: 2 (shown below). After many rolling updates, what does this field control?
An attacker has a list of thousands of valid usernames for a company SSO portal. Rather than trying many passwords against one account, they try a single common password such as "Spring2026!" against every username, wait a few hours, then try a second common password against all of them. What is this technique, and why does it slip past typical lockout defenses?
What does this Go program print?
What is the resolved type of `Greeting` below?
What does this code log to the console?
A namespace has the LimitRange below. You then create a Pod whose container specifies NO resources.requests or resources.limits at all. What happens?
An attacker takes a large list of username/password pairs leaked from a breach of one website and uses automated tools to replay those exact credentials against the login forms of many unrelated sites, gaining access wherever a user reused them. What is this attack called?
What does this Go program print?
What is the resolved type of `Grades` below?
What does this code log to the console?
You create the Role and RoleBinding below in the dev namespace, granting user jane permission to list Pods. jane then runs `kubectl get pods -n prod`. What happens?
A site loads a JavaScript library from a third-party CDN. Which mechanism makes the browser refuse to execute the file if the CDN was compromised and the file's bytes were altered?
What does this program print?
What is the resolved type of `T` below?
What does this code log to the console?
What does a Kubernetes DaemonSet guarantee about where its Pods run across the cluster?
Why is a unique, random salt added to each password before hashing?
What does this program print?
Given the snippet below, which statement about how TypeScript type-checks these two calls is correct?
What does the following expression evaluate to?
Which Kubernetes Service type exposes the Service only on an internal cluster IP, making it reachable from inside the cluster but not from outside?
In information security, what does the principle of least privilege state?
What does this Go program print?
What is the result of running this TypeScript code through the compiler?
What does the following code print?
In Kubernetes, what is the smallest deployable unit you can create and manage?
Which approach correctly prevents SQL injection in this Python database query?
What does this Go program print?
What does the `readonly` modifier do when applied to a class property in TypeScript?
What is logged by these two comparisons?
What does this code output?
What does this code print?