"Typo" has been a word of its own for a very long time. Even were it not, wouldn't it look odd to see it written typo'? Since you don't, you don't use the apostrophe in a pluralization, either. When it was still "hip slang," lo these many years ago, there was a period after it, which was, as I recall, put at the end for a typo, as in "typos." and not "typo.s," which, as you see, looks ridiculous.

But, yes, "others' typos" is perfectly correct.

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Gillian

"Now everyone was giving her that kind of look UFOlogists get when they suddenly say, 'Hey, if you shade your eyes you can see it is just a flock of geese after all.'"

"You can't erase icing."

"I can't believe it doesn't work! I found it on the internet, man!"