The lady who was seen taking photos of them, posted one herself! She seems to be one of Yunho’s 85 club friends as she was present in several meetings (e.g. here and here) and also took photos with enlisted Changmin and Donghae before~

https://www.instagram.com/p/BRU4XLGgO-3/

Translation:

she only delivered the 🎂 & stayed to take the photos as it was bromance timeㅋ

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Credits:

Lee Sihyun’s Instagram (sihyunlee0924),
Translated by @snxy,
Posted and Shared by TVXQ! Express