diff -r 058bb3dc685f -r 0b59724cb3f2 cubicweb/misc/migration/3.15.4_Any.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/misc/migration/3.15.4_Any.py	Sat Jan 16 13:48:51 2016 +0100
@@ -0,0 +1,13 @@
+from __future__ import print_function
+
+from logilab.common.shellutils import generate_password
+from cubicweb.server.utils import crypt_password
+
+for user in rql('CWUser U WHERE U cw_source S, S name "system", U upassword P, U login L').entities():
+    salt = user.upassword.getvalue()
+    if crypt_password('', salt) == salt:
+        passwd = generate_password()
+        print('setting random password for user %s' % user.login)
+        user.set_attributes(upassword=passwd)
+
+commit()