We have been having this issue for a while, and our hosting provider is unsure of it as well as the server has had Java and CF updates and patches, but it still occurs. We have looked at all of the online resources we could find, but can't find anyone else with a similar issue. We have a SIMPLE ColdFusion created CAPTCHA on our site and we notice that about 1 in 20 images has a UNIQUE character within the image. We have tried to narrow it down but the only thing we can determine is it is based on an 'Arial' font that is being used. Each time it shows up the unique character is different, so not always the 'r' or something like that. We have tried using ' fonts="Times New Roman" ' or another font, but that seemed to work for a while, but now anytime we specify the font, the CAPTCHA no longer displays ( not errors...but it ends the code at that point ). So we currently had to remove the font to get it to work. The character looks like a bunch of lines ' |||| ' so it is impossible to tell what it could be as there are no ( I, i, l, L, 1 ) in the character list script. I am really wanting to get this corrected for not only our customers, but for our hosting company as well as they have spent hours trying to debug this as well. Thank you everyone for your thoughts and suggestions with this issue! ( Here are 2 samples of the character that we are seeing ).
How many characters do you expect each captcha to show?
To test, I copied Ben Nadel's code from https://www.bennadel.com/blog/873-using-captcha-in-coldfusion-8.htm and ran it as a CFM page. The only change I made was to set the font to 'arial' and reduce the number of characters to 5.
To generate new captchas, I just kept pressing F5 to refresh the page. After hundreds of tries I could not reproduce your lines '||||' even once.
I can see now that there are no ribbons in your pictures. Whereas most of the captchas I generated had ribbons, like the one below. So, could it be that some bug in your system is lumping the ribbons into ||||?
Test to find out which letters pass as a successful response when the captcha includes ||||.