"403 Forbidden" error when posting

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rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
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"403 Forbidden" error when posting

Post by rjlittlefield »

We've had a few instances lately where people have gotten "403 Forbidden" errors when posting.

Those errors result from a false positive detection, when the content being posted happens to match one of the unknown but probably arcane content filtering rules that our hosting service has recently put in place.

We presume that the rules are intended as a defense against certain types of attacks against websites, for example "cross-site scripting" malware.

However, sometimes the rules match things that are in fact completely innocuous. As an example, it turns out that at this moment the sequence
<newline>Move<space>

results in a "403 Forbidden". Apparently it's forbidden to move! Or something like that... (I have no idea what the rule might be intending to defend against.)

Anyway, if you get one of those "403 Forbidden" errors, the only known solution is to use Preview, in combination with something like binary searching your post content, to find the snippet that's causing the problem and change it to something that does not cause the problem.

In the case of <newline>Move<space>, changing the text to
<newline><space>Move<space>
avoids the 403 Forbidden, while producing exactly the same output.

When you get caught by one of these, please let Admin know what you ran into. Sending email to administrators@photomacrography.net is a good method of sending stuff that you just can't make work. Don't try using the Contact form. That will have the same underlying problem, but with an even more confusing message: "Form PHP script is missing from web server, or PHP is not configured correctly." (Sigh...)

--Rik

Grahame
Posts: 60
Joined: Tue Sep 30, 2014 11:36 pm
Location: New Zealand

Post by Grahame »

Just had another myself.
It was
? space roll eyes emoticon that caused the 403, also wouldn't let me preview.
?roll eyes, was acceptable.
It's a weird one.
Last edited by Grahame on Sat Jun 03, 2017 9:18 pm, edited 1 time in total.

rjlittlefield
Site Admin
Posts: 23562
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Post by rjlittlefield »

? space roll eyes emoticon that caused the 403, also wouldn't let me preview.
The filtering appears to be done without regard to URL, so I would expect it to do the same thing for Preview as for Submit, and for that matter Search.

But I cannot reproduce 403 with the pattern I think you've described.

? :roll:

Maybe some other punctuation involved?

--Rik

Grahame
Posts: 60
Joined: Tue Sep 30, 2014 11:36 pm
Location: New Zealand

Post by Grahame »

Hello ? :roll:

Edit
Hmmm just gave it a test, worked that time.
Weird I just changed one thing at a time till I got it to work.
The internet never surprises me when it breaks, it surprises me when it works :D
Have a good one Rik

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