Root-Cause & Secure-Code Remediation: CVE-2025-31131
Fix CVE-2025-31131 at the source. Read the vulnerable YesWiki template loader, see how the squelette value is concatenated into the file path (CWE-22), reject a dot-stripping attempt, deploy a validated loader (basename + extension allowlist + realpath), add a WAF rule, and verify with audit and vulnscan.
Skills you will practice
- Secure software design
- path-traversal defense; File read / traversal
- root cause and remediation; Secure architecture and input trust boundaries
Certifications this lab maps to
This lab builds hands-on skills that appear on these certification exams. thinQtank Learning runs instructor-led training camps for each — click one to see upcoming classes.
The scenario
Triage upgraded YesWiki; IR handled the breach. You are the security engineer who has to fix the loader and add an edge control. Start at the source.
What you will do
- Understand the root cause4 steps
Open the source · Read the root-cause note · Read the vulnerable loader · What is the sink?
- Audit and reject the weak fix4 steps
Audit the vulnerable file · Read the proposed fix · Audit the weak fix · Why is the blacklist insufficient?
- Apply the fix and add a WAF rule8 steps
Read the correct fix · Audit the correct fix · What makes it safe? · Deploy the fix · …
- Reason and document4 steps
Verify the deployed loader · Two layers · Write the PR note · The principle
How this lab works
A real Linux-style console. Commands run against real files, so hashes, hex dumps and comparisons give real results.
A file browser where you can place evidence into the lab, either the file provided or one of your own.
Reset a single step, a whole task or the entire lab. The environment is rebuilt so you can try again cleanly.
Progress saves after every step. Close the tab and come back later; your files and answers are waiting.