Instruction: Answer the given question by extracting information from the supporting document.

Input:
Question: Does this leak?
Document: Get leak proof, then you don't have to worry about other people knocking hot, sticky (unless I drink tea), liquid all over the place.
Aside from this flaw, the mug is comfortable and holds a good amount of liquid. However, it will leak if you're not careful. The cap does not screw in, but rather presses on. My quest for a proper travel mug continues.
This is absolutely the best stainless tumbler you will find. It keeps cold drinks that way for hours as well as a hot drink hot. The only drawback is that it could leak if you need it airtight. Otherwise, just perfect. I've ordered these for my family members and they all agree.
If you fill the tumbler totally full with hot coffee or tea and then drive in a car with it in the cupholder, the shaking of the tumbler can cause it to leak some fluid through the top and sides of the lid. And if you tip the tumbler downward towards you mouth to drink while driving, be VERY CAREFUL!
It also keeps things HOT, rubber grip, spill-proof lid and SCREW ON lid... Thermos...If you add the screw on no leak lid, you have a winner. I will pay good money for a mug that performs, so I will continue on my search.. Hope this helps..
I own four of these travel tumblers. This is a great travel tumbler if you do a few things:1) Drill a very small hole (1/16) in the top of the lid to allow for air flow. The small adjustment significantly improves the liquid flow and essentially will not leak.2) Never wash it in the dish washer. The dish washer will cause the lid seal to weaken.
... and if it was a minor bump, the lid will leak thru the removable (to clean) slider/closer. So, its very awkward in how it must be handled. An email to Thermos regarding the quality of this has gone unanswered. I love the mug, the color, style the feel in my hands, fits the cupholder great, but these short-comings are just too much to enjoy it. I will seek out a discontinued Starbucks Curve Mug (which my wife has).
The lid is easy to use/clean and stays in place perfectly for my uses. It is not meant to be spill-proof, so you can't tip it on its side and expect it not to leak. It is however quite nicely spill-resistant. It feels nice in the hand and is well made. I would recommend this to anyone looking for a travel tumbler that doesn't need to be spill-proof. I think that would be the only reason someone wouldn't like this.
The colors you can choose are beautiful. I love love love this mug and after trying  numerous types, this is the one I have settled on as the mug of choice. I see other reviews that indicate that the mugs get wobbly, but I swear I have never had this problem. The mug lid is secure once it's on. I have had the screw on types before, and those leak too if you don't screw them on properly. I just enjoy the convenience of a pop off lid.
I purchased this mug for my son. We are both coffee lovers and seldom are we found without a cup in our hands. I was given one of these Thermos mugs as a gift two years ago and based upon my experiences it was a no-brainer to order one for him. I've gone through dozens of different mugs over my years and my biggest complaints have been that they either leak/drip coffee or the liquid doesn't stay hot long enough.
Answer: Well you definitely can't turn it upside-down and if it falls on its side, yes it does. I think that just about any thermos designed to be drunk from has this problem. But during normal use (bringing it up to your mouth, tilting it to drink from it) mine hasn't leaked.