Hidden knowledge as a Quranic term is only for Allah but there is a kind of knowledge which Allah shares with particular groups.
It is very important to know the attributes of Allah, in order to improve those attributes and also it can provoke us to avoid the forbidden actions. For instance when we read in the Quran:
Certainly We have created man and We know to what his soul tempts him, and We are nearer to him than his jugular vein[1]
we would be carful in our thoughts and deeds. This verse asserts that the knowledge of Allah covers everything even what comes to our minds and He is near to us as it is possible.
This verse of Quran indicates the depth of relationship between creator and creatures. Considering of this significant point can give a rise to eschew forbidden deeds, particularly, as we read in the next verse that two angels are accompanying us writing our deeds and also we know that they will testify before Allah in the hereafter.
Moreover Allah knows everything, He watches us and on the other side we must know that we are under constant close surveillance day and night. In short, we are before Allah the almighty. As Imam Baqir (a.s) states in a narration that unseen and seen are the same before Allah[2]. Similar meaning is mentioned in the Quran as well:
With Him are the treasures of the Unseen; no one knows them except Him. He knows whatever there is in land and sea. No leaf falls without His knowing it, nor is there a grain in the darkness of the earth, nor anything fresh or withered but it is in a manifest Book[3]
Hidden knowledge (ilm al-Qayb) is one of the points presented in this verse. The verse clearly states that the treasures of the Unseen are with Him and no one knows them except Him, hence Allah alone has the hidden knowledge. But on the other side, by some of the Quranic stories it can be proved that prophets had some kind of hidden knowledge as it seems reasonable for successors of the prophet Mohammad (s). Imam Baqir (a.s) unraveled this point in a narration by saying Allah has a type of knowledge which no one knows it and He has a type of knowledge which close angels, prophets and we know that.[4]
As a result, the hidden knowledge as a Quranic term is only for Allah but there is a kind of knowledge which only Allah, close angels, prophets and household of the prophet know it.
Notes:
[1] Quran 50:16 وَ لَقَدْ خَلَقْنَا الْانسَانَ وَ نَعْلَمُ مَا تُوَسْوِسُ بِهِ نَفْسُهُ وَ نحَنُ أَقْرَبُ إِلَيْهِ مِنْ حَبْلِ الْوَرِيد
[2] Commentary of Qommy (TAfsir Qommy). V 1. P 360. السر و العلانیه عنده سواء
[3] Quran 6:17 وَ عِندَهُ مَفَاتِحُ الْغَيْبِ لَا يَعْلَمُهَا إِلَّا هُوَ وَ يَعْلَمُ مَا فىِ الْبرَّ وَ الْبَحْرِ وَ مَا تَسْقُطُ مِن وَرَقَةٍ إِلَّا يَعْلَمُهَا وَ لَا حَبَّةٍ فىِ ظُلُمَاتِ الْأَرْضِ وَ لَا رَطْبٍ وَ لَا يَابِسٍ إِلَّا فىِ كِتَابٍ مُّبِين
[4] Touhid of Sadooq. P 138. ان لله لعلما لا یعلمه غیره و علما یلعمه ملائکته المقربون و انبیائه المرسلون و نحن نعلمه