Step 1: Find a Strider with a saddle.
Step 2: Go to "sneaking mode" by using shift button.
Step 3: Try to right-click on Strider as to remove the saddle.
This will start an attempt to mount the Strider, but, because shift button is pressed, you will dismounted (and you will fall in lava in the worst case).
In some cases if you try to mount the strider again this will block you from interact with the world, as you actually mounted the Strider, but buggy.
You will fall in lava but you will not die.
Related issues
Comments

Trying to mount a Strider with shift button pressed cause that you will dismounted, but if you keep shift button pressed (after auto-dismounted), and try to mount the Strider again, this will cause MC-175999.

Thank you for your report!
We're actually already tracking this issue in MC-173404, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki
Do striders even have an inventory?