The user's manual of my car contains the following warning:
Do not add washer fluid when the hybrid system is hot or operating as washer fluid contains alcohol and may catch fire if spilled on the engine etc.
Is this really the case? I think the scenario might be possible if you spill a lot of washer fluid on a hot engine, as alcohol in the mixture evaporates faster than water, so if you happen to have a static electricity spark, it could theoretically ignite the evaporated alcohol from the washer fluid.
However, I find it hard to believe someone could spill so much washer fluid on the engine that this scenario is even a remote danger.
If the interpretation of the warning is taken to the extreme, it means you cannot add more washer fluid if you run out of washer fluid on a long trip!
From Wikipedia, you can see the flash points of alcohol-water mixture.