we will solve packer form picoCTF

download the binary and run file on it

it’s a normal ELF 64-Bit binary

now let’s run UPX on it

upx -d ./out

notice that the file was unpacked

now let’s run strings on it

strings out | grep -i flag

now we got this hex decimal value

now let’s go to cyberchef to decode it

picoCTF{U9X_UnP4ck1N6_B1n4Ri3S_1a5a3f39}

Amazing we got the flag!