Hello everyone,

I'm getting some troubling reports from various users, who say that they're getting reports from members of their list that unsubscribe from a newsletter, or to be resubscribed, then unsubscribed, etc in a huge loop

The usage log will look a lot like this:

[Tue May 3 16:28:33 2011]    listshortname   12
123
12
12    Unsubscription Confirmation Sent for listshortname
list     hapless
email@example
com
[Tue May 3 16:28:33 2011]    listshortname   12
123
12
12    Unsubscribed from listshortname
unsub_confirm_list  hapless
email@example
com
[Tue May 3 16:28:33 2011]    listshortname   12
123
12
12    Subscribed to listshortname
unsub_confirm_list  hapless
email@example
com

[Tue May 3 18:41:15 2011]    listshortname   12
123
12
12    Unsubscribed from listshortname
unsub_confirm_list  hapless
email@example
com
[Tue May 3 18:41:15 2011]    listshortname   12
123
12
12    Unsubscribed from listshortname
list    hapless
email@example
com

[Tue May 3 21:13:34 2011]    listshortname   12
123
12
12    Unsubscribed from listshortname
sub_confirm_list    hapless
email@example
com
[Tue May 3 21:13:34 2011]    listshortname   12
123
12
12    Subscribed to listshortname
sub_confirm_list    hapless
email@example
com
[Tue May 3 21:13:35 2011]    listshortname   12
123
12
12    Subscription Confirmation Sent for listshortname
list   hapless
email@example
com

[Tue May 3 22:22:35 2011]    listshortname   12
123
12
12    Unsubscribed from listshortname
sub_confirm_list    hapless
email@example
com
[Tue May 3 22:22:35 2011]    listshortname   12
123
12
12    Subscribed to listshortname
list    hapless
email@example
com

And this pattern will continue to repeat

The first chunk of code is what's supposed to be logged when someone requests to unsubscribe

The second chunk is when what's supposed to be logged when someone confirms the unsub

The third chunk is when someone requests to be subscribed

and the forth chunk is when someone confirms the subscription

Everything looks great, except that the user isn't doing any of this - it's all on autopilot and this pattern will continue to repeat and repeat and repeat, until the list owner finally just removes the email address from the list, permanently

I'm scratching my head at what the base problem is and I currently have absolutely no idea

My first thought was that it's some sort of Denial of Service attack, but it would seem strange to have it target a specific email address that was already subscribed and then have the "attack" span over hours Not a very good attack! This would also mean the pin verification system has been broken, but I'm not sure that's the case, either

My next suspicion, which is a good one, is that there's a bug in Dada Mail, but all my looking hasn't turned up with anything

My most recent suspicion is that it's some sort of auto link prefetching going on with the user's email reader Link prefetching is a really bad idea for email messages, exactly for this reason, but would explain the mechanism that causes this loop:

When a subscriber receives a confirmation email to unsubscribe, it gets followed automatically and they will receive a, "you've been unsubscribed" email, which has a link to subscribe again, which will be followed, automatically, which will send the subscription confirmation email, which will subscribe them That'll send a "you're now subscribed" email, which has a link to unsubscribe them again - and that's where the loop is

That's my current theory

Has anyone on this list experience this problem? Got any other idea what may be going on?

It's very strange, since it happens to maybe 1 out of every 10,000 subscribers The link prefetching could be a sign that the user's machine has been comprised with some sort of virus and this is just a weird side effect of some sort of logging system of the virus itself - I dunno I could really use some help to get to the bottom of all this, though,