The iOS 11.2.5 beta 6 update appears to fix a bug that allowed a malicious link to freeze the Messages app on iOS devices. More updates you could check news on 3uTools.

Apple has just released iOS 11.2.5 Beta 6 for registered developers. Here’s how you can download it right now.

You're suggested to back up your iDevice first, just in case. 

Step1: Connect your iDevice to PC using the USB cable and launch 3uTools on your PC. 

Step 2: You could upgrade in Easy flash directly without losing data. Click "Flash & JB" -> "Easy Flash", then select iOS 11.2.5 beta6, finally click "Flash".

 If you want to save iDevice's data, you need to select the checkbox that "Retain User's Data While Flashing"

Alternatively, you can also import the downloaded firmware in Pro Flash, as below.

Step3: Keep a good connection between iDevice and PC, and then just wait patiently till this process is finished. The whole flashing process needs 5~10 minutes in general, when it's finshed, then you can experience iOS 11.2.5 beta 6 freely.