• Open a dockerfile in VSCode (uses the latest textmate grammar from https://github.com/moby/moby/blob/master/contrib/syntax/textmate/Docker.tmbundle/Syntaxes/Dockerfile.tmLanguage)
• Write the following and observe to first escaped quote not being registered thus throwing off the syntaxic coloring of the rest of the document :

RUN echo //blep.derp.com:9875/:_authToken=\"er99iWoLDerYl666YRUS134YfEghohhrrrr516LwfM=\" >> ~/.npmrc

Fun fact, if you write the same line twice, the second time both quotes will be registered correctly

Copied from original issue: microsoft/vscode#46419