Changes have been made in Git (FRAMEWORK_5_2):

commit f298a21f61dc2097e39ffae90b4062b2a85dee90
Author: Jan Schneider <jan@horde.org>
Date:   Mon, 11 Jul 2016 17:49:20 +0200

[jan] Fix losing shared users when adding invalid user name (Bug #14415).

  M docs/CHANGES
  M js/kronolith.js
  M lib/Ajax.php
  M package.xml

https://github.com/horde/kronolith/commit/f298a21f61dc2097e39ffae90b4062b2a85dee90

Changes have been made in Git (master):

commit 3a827c52b502f85fff44ef38d18a5f949c5c2519
Author: Jan Schneider <jan@horde.org>
Date:   Mon Jul 11 17:47:40 2016 +0200

     [jan] Fix losing shared users when adding invalid user name (Bug #14415).

  kronolith/js/kronolith.js | 21 +++++++++++++++++----
  kronolith/lib/Ajax.php    |  1 +
  kronolith/package.xml     |  2 ++
  3 files changed, 20 insertions(+), 4 deletions(-)

http://github.com/horde/horde/commit/3a827c52b502f85fff44ef38d18a5f949c5c2519

Changes have been made in Git (FRAMEWORK_5_2):

commit c7d739e5403688f6e3fd81c6db7ddce70be3b5f9
Author: Jan Schneider <jan@horde.org>
Date:   Mon Jul 11 17:47:40 2016 +0200

     [jan] Fix losing shared users when adding invalid user name (Bug #14415).

  kronolith/docs/CHANGES    |  1 +
  kronolith/js/kronolith.js | 21 +++++++++++++++++----
  kronolith/lib/Ajax.php    |  1 +
  kronolith/package.xml     |  2 ++
  4 files changed, 21 insertions(+), 4 deletions(-)

http://github.com/horde/horde/commit/c7d739e5403688f6e3fd81c6db7ddce70be3b5f9

Adding external (or invalid/non-existent) email accounts to a shared 
calendar within Horde, will wipe out any other valid accounts after 
the external account you just added.

This is bad because if you have say for example 50 addresses already 
set and you accidentally add an invalid address at the beginning (or 
somewhere in the middle), it would wipe everything out after that 
address.  There are no warnings, there are no errors, it just wipes it 
out.

Steps to reproduce:

1) Create several email accounts under a single domain name.
As an example I have testing@cptest.tld and added: 
billybob@cptest.tld, user1@cptest.tld, user2@cptest.tld and 
user3@cptest.tld.
2) Go to Horde for testing@cptest.tld and click on Calendar button at top.
3) Go to My Calendar on the left-hand side and click the Pencil icon.
4) Click on Sharing tab and select "Share with the users:"
5) Enter billybob@cptest.tld, user3@cptest.tld, user1@cptest.tld, 
user2@cptest.tld
Click Save.
Everything saves just fine and if you come back in, they are all still set.
6) Now add cpanelnoreply2016@gmail.com in-between user3@cptest.tld and 
user1@cptest.tld
Hit save.
7) Now come back in and notice that the only accounts left are 
billybob@cptest.tld and user3@cptest.tld (cpanelnoreply2016@gmail.com 
and the other 2 are now missing).

Suggested resolution:

First, It should really say "comma separated". Additionally it should 
also say something along the lines of "This is for Horde users within 
your domain only, External accounts cannot be added"

Barring that, it should either not add the invalid account 
(cpanelnoreply2016@gmail.com) at all, but leave the rest intact, or it 
should warn you upon saving that the address you just added is invalid 
and discard your changes.