Image on left is from 4 days ago, but the pimple was slowly forming over around 2 weeks.
The goop was sticky, not oily. Earphones are Panasonic RP-TCM130.
I was not able to find an explanation.
Something to increase cable lifespan, lubrication, rubber disintegrating, sweat and earwax that somehow got into the cable, dielectric grease, SCP-1407, no clear answer.
At first I thought the wires just somehow twisted. Nope.
These are earbuds, not big ass speakers. There shouldn't be enough power going through those cables to do melt anything.
You would be incorrect. If the power source shorts, it would heat the wires sufficiently.
And how much power do you think the DAC in a phone is going to output?
The built in DAC in a phone can barely drive my headphones, let alone melt a silicone cable. They typically output less than a watt. On a good day. Rubbers melting point is 365c and 1 watt isn't gonna do that.
It's more to do with wire gauge...