WeChat can access the following on your device:

In-app purchases
Device & app history

• retrieve running apps

Identity

• add or remove accounts
• find accounts on the device
• read your own contact card

Contacts

• read your contacts
• modify your contacts

Location

• approximate location (network-based)
• precise location (GPS and network-based)

SMS

• read your text messages (SMS or MMS)

Photos/Media/Files

• read the contents of your USB storage
• modify or delete the contents of your USB storage

Camera

• take pictures and videos

Microphone

• record audio

Wi-Fi connection information

• view Wi-Fi connections

Device ID & call information

• read phone status and identity

Wearable sensors/Activity data

• body sensors (like heart rate monitors)

Other

• download files without notification
• read Home settings and shortcuts
• receive data from Internet
• connect and disconnect from Wi-Fi
• read sync settings
• create accounts and set passwords
• control vibration
• modify system settings
• measure app storage space
• prevent device from sleeping
• set an alarm
• view network connections
• toggle sync on and off
• install shortcuts
• access Bluetooth settings
• pair with Bluetooth devices
• run at startup
• change your audio settings
• draw over other apps
• use accounts on the device
• control Near Field Communication
• full network access
• send sticky broadcast
• uninstall shortcuts

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Last Update: 06/12/2015

Source:
https://play.google.com/store/apps/details?id=com.tencent.mm