BUUCTF: [BJDCTF2020] Guess what I am

Title address: https://buuoj.cn/challenges#[BJDCTF2020]%E4%BD%A0%E7%8C%9C%E6%88%91%E6%98%AF%E4%B8%AA%E5%95 %A5

010 EditorOpen and found the file header is pngthe

Modify the suffix to .pngget a QR code, the scan result is as follows:

010 EditorOpen direct search for text charactersflag

flag{
    
    i_am_fl@g}