Fire starting in toilet since Dec. 2020 update

@savedasims : Also, according to the patch notes for 1.65.70 (Nifty Knitting Stuff pre-patch from July 23rd, 2020)...

• Has this ever happened to you? Your Sims are in the privacy of their bathroom, and suddenly there is the smell of smoke? If your Sims have experienced a... “burning sensation” while satisfying their Bladder need - no more! Thanks to F1xABuG*. F1xABuG deals with all symptoms of flammable bladder functions, patch today!

*F1xABuG will not relieve all fire related incidents while in the bathroom, Sims still will possibly experience flammable encounters if they are Angry or have had Spicy Food. Fire may also still be experienced if Simmers have installed Eco Lifestyle and choose to Compost upgraded toilets with no Insect Farm on Lot. F1xABuG is not responsible for any other side effects, such as Reticulating Splines.

Are Angry moods and/or spicy food possibly involved, too?

Apparently I did without reading the details. Now I feel like an idiot.

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.72.28.1030
What expansions, game packs, and stuff packs do you have installed? all of them
Steps: How can we find the bug ourselves? by using the toilet
What happens when the bug occurs? toilet on fire
What do you expect to see? toilet on fire
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? Yes
Please describe the patch or change you made. the pach that aded bunk beds

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I do not have any recordings but every time I wach youtube the toilet caches on fire

This happens if you have Eco Lifestyle.

If you have a Sim with the "handy" trait from finishing the Nerd Brain aspiration and they instant upgrade the toilet, it applies the "composting container" upgrade.  Or you might have added that upgrade manually.  Either way, that toilet almost certainly has a composting contaner. 

If you have a composting container and don't remove the compost the toilet catches fire.  The option to remove the compost doesn't appear unless you have an insect farm, however. 

If anyone wants to see this in action, LilSimsie's short lifespan legacy includes one of these toilets. 

@acoxshesIf you're not sure if you have the composting container, click upgrade and see if that option is already checked off.

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Occasionally (10% - 49%)
What is your current game version number? 1.73.57.1030
What expansions, game packs, and stuff packs do you have installed? Most of them. I'm just missing snowy escape and a few stuff packs.
Steps: How can we find the bug ourselves? My sim pees.
What happens when the bug occurs? The toilet and surrounding area, as well as my sim, set on fire.
What do you expect to see? He probably shouldn't light on fire while he's peeing.
Have you installed any customization with the game, e.g. Custom Content or Mods? Not now. I've removed them.
Did this issue appear after a specific patch or change you made to your system? No

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It would just be nice to have my sim pee in peace...