Some have a custom to bake challah with a key inside it (or challah in the shape of a key) the Shabbat following Pesach. This has never been my custom (or my family's custom) nor have i ever lived in a community where the custom was widespread. Nevertheless, with the internet (and particularly facebook) minhagim which were once specific to a certain community are now shared around the world.
My daughter asked me the reason for this custom. And I didn't know.
I wonder if it is a way of reminding people to upgrade their internet security and passwords on the eve of a potential massive cyberattack on Israel (secheduled for Sunday)
However, even with their ruach hakodesh, I doubt that the originators of this minhag had cyberattaks in mind. So I drew a blank. Luckily Hashem gave us google for such times of crisis, so I did a search. Here are four results that I found, each with a very different view of the custom.
Rabbi Prero describes his wife hunting for hours to find dough to make schlissel challah.
A Simple Jew (guest post) has 10 reasons for putting the key in the challah, plus different ways of making the challah.
Rabbi Slifkin explains that even though in general he is not against customs which seem based on superstition, in this particular case he is concerned because of the message regarding parnassa that it gives to an already desparate socio-economic group.
And Rabbi Shelomo Alfassa explains the pagan background to the custom and conludes that it has nothing to do with Judaism.
I'll leave the last word to Rabbi Shlomo Aviner who was asked about this custom:
Q: Is there an authentic source for making Challah with a key in it (or in the shape of a key) on the Shabbat after Pesach as a Segulah for Parnasah, or is it superstition?
A: It is not forbidden but there is no meaning in doing so (this custom is mentioned in Ta'amei Ha-Minhagim pp. 249-250).