Oh, I see, it really is prompting to fill in these raw strings, but it is prompting for two fields at the same time.

OK, I give up. You can explore the form in question at
https://www.traffic.taichung.gov.tw/mail/index.asp?Parser=99,9,68,66

To reproduce it you have to have used the form several times.
So if you can't reproduce it right away, just close this bug.

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It prompts with items it plans to fill in to fields other than the one it colored blue in the first place.

Tried testing the issue on reported chrome version #70.0.3538.102 using Ubuntu 17.10 by following steps as per comment#0, following are the observations noted while testing the issue.

Observations:
===========
1.After filling the email id in "*電子信箱：" textbox then after clicking "*密　　碼：" found that there are already suggestions of previously saved passwords. After selecting one of them observed that the value in "*電子信箱：" did not change.
2.Reloaded the page and entered an email id in "住　　址：" textbox, then on selecting a value from suggestions of previously saved passwords in "*確認密碼：" , the value of "住　　址：" did not change.
3.When filled the value in "*確認密碼：" from the suggestions of of previously saved passwords, then automatically in  "住　　址：" email value assosciated to the selected password got filled in.
4.Unable to see "Fill in password related to:" at the top line.

Attached screencast for reference.
@reporter: Could you please let us know if anything is being missed here.
Thanks.!

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Currently here is my strategy with this form:
$ mech-dump https://www.traffic.taichung.gov.tw/mail/index.asp?Parser=99,9,68,66
  cname=   (text)     5. click to autofill.
  tel=     (text)     6. this gets autofilled.
  email=   (text)     4. this gets autofilled.
  address= (text)     2. this gets autofilled, but wrongly with my email. 7*
  pwd=     (password) 3. click to autofill.
  chk_pwd= (password) 1. click to autofill.
*now erase, and click to select proper address.

Anyway, we see the problem is just too complex. So maybe just give up
on this bug.

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot