Looks like you better be careful on downloading what appears to be a harmless gif, especially sent by someone unknown. A major security flaw in Whatsapp has been discovered, which allows hackers to hijack people's phones by sending them a gif. This bug allows hackers to steal files and view chat messages from compromised Android devices.
This bug was discovered by a researcher named Awakened, who pointed out that this bug is triggered if a user opens a specially-created gif in the messaging app. Funnily enough, this is likely to work well for phones and devices running Android 8.1 and Android 9, though is less affective with older versions of Google's operating system, so if you have an older device, you're safe. Not to say that it won't work, rather the app crashes before it could reach a point that could control the PC register.
A fix is already available so you will need to update your Whatsapp app (2.19.244 or above) ASAP to avoid falling victim to this.
It's also worth noting that WhatsApp wasn’t aware of any users falling victim to the attack. “This issue was reported and quickly addressed,” a spokesperson told The Sun. “We have no reason to believe this affected any users though of course we are always working to provide the latest security features to our users.”