Stegano in the world of attack and defense

It's a pdf file

Open it first

A bunch of English letters, nothing , Tip no flag 了

Then use notepad++ Look at the file

Ctrl+F Quick search flag

 

  Found something , The coding tail in the back has = Number , The approximate rate is base64

Copy the past and decode

emmm, Good guy, this is not flag

Find out if there is anything special

  Only to find the difference here , Think about it PDF Steganography , Transparent words ....

Open the file with a browser , See if there is any copy empty

Sure enough , In the first line, there is something fishy

  Copy down , Paste into an empty file

emmmm, Let's copy the full text directly

  Sure enough, I found something different in the second line

Only AB Code for , Think of the previous discovery tips AB .-

It should be Morse code , hold A Switch to .  ,  hold B Switch to -

Decoding will OK 了

On the text editor , Delete except AB All codes outside , Then use the built-in replacement function , Replace all symbols

 

  Copy to the website for decoding

  obtain

CONGRATULATIONS,FLAG:1NV151BL3M3554G3

  Change the format to submit OK 了