Via the Steam Store:

An update to Team Fortress 2 has been released. The update will be applied automatically when you restart Team Fortress 2. The major changes include:<br/> <ul style="padding-bottom: 0px; margin-bottom: 0px;" ><li>Fixed a client crash related to viewing notifications <li>Fixed being able to interrupt taunts using the ConTracker commands <li>Fixed a bug with the Medi Gun not staying attached to players <li>Fixed a bug with the Backburner using its owner's angle to determine whether the attack is behind the victim <li>Fixed a rendering issue with the Spectral Swirl unusual effect <li>Fixed not being able to fire the Dragon's Fury in some areas (e.g. the control point on Nucleus) <li>Fixed not being able to light Huntsman arrows with the Dragon's Fury <li>Fixed Dragon's Fury projectiles not fizzling when hitting water <li>Fixed not being able to detonate stickybombs when switching to melee with secondary attack held down <li>Fixed the charge sound for the Stickybomb Launcher not stopping if the player switches weapons while charging <li>Fixed Quick-Fix Medics not properly following/mirroring the Pyro after launching with the Thermal Thruster <li>Fixed being able to shoot flares through objects like setup gates <li>Fixed the Pretty Boy's Pocket Pistol always giving 7hp per-hit <li>Fixed the Winger not counting towards the Scout achievement "Gun Down" <li>Fixed the Festive Sandvich not counting towards the Heavy achievement "Konspicuous Konsumption" <li>Fixed the Rescue Ranger not counting towards the Engineer achievement "Texas Two-Step" <li>Fixed the Genuine version of the Flying Guillotine having no taunt <li>Updated the Vita-Saw so victims spawn random internal organs on hit <li>Updated the Atomizer damage penalty vs players to -15% (from -25%) <li>Updated the party system so invites are shown to all party members <li>Updated the Thermal Thruster stomp damage on other players to be 3x the base fall damage - not the reduced fall damage of the owner <li>Updated the "With Friends Like these..." achievement to check for five friends instead of seven <li>Added the Heals for Reals 2017 community medals <li>Added the "Philanthropist's Indulgence" community medal for Random Acts of TF2 <li>Added the "Spectral Snowflake" community medal for the Nightmare Before Smissmas 2017 community showcase </ul>