Step 1: Simple Substitution

Encoded message:

URYYB JBEYQ

Step 2: Hex XOR Decryption

Decrypt the hex string XORed with key 0x55:

3B 34 37 37 21 2E 20 35 3D 2D 21
    

Step 3: Base64 Decode

Decode this Base64 string:

ZWNyeXB0X3RpbWU=

Final Step: Enter the Hidden Flag

Combine previous answers to form the flag in the format: flag{part1_part2_part3}