Redaction gone wrong | picoCTF 2022 Solutions

Description

Sensitive text in a PDF was only visually redacted. Convert the PDF to text (or copy/paste) to reveal the hidden flag.

Setup

Install `pdftotext` (from poppler-utils or xpdf).

Run `pdftotext Financial_Report_for_ABC_Labs.pdf` to create a .txt version.

Search the text output for `picoCTF` (or simply copy the blacked-out text directly inside a PDF viewer).

pdftotext Financial_Report_for_ABC_Labs.pdf

grep -oE "picoCTF\{.*\}" Financial_Report_for_ABC_Labs.txt

Step 1Convert the PDF
Visual redactions don’t remove the underlying text. `pdftotext` extracts everything, including the supposedly hidden sections.
Step 2Search for the flag
Grep the generated text file for picoCTF to immediately locate the flag string.

picoCTF{C4n_Y0u_S33_m3_f...}

Real-world lesson: always remove sensitive text entirely before distributing redacted documents.