Issue #2599442 by jhodgdon, heykarthikwithu, Himanshu5050, eojthebrave, metzlerd: Document common form/render element properties

Issue #2554219 by nod_, larowlan, tim.plunkett, regilero, droplet, japerry, samuel.mortenson, Pere Orga, effulgentsia, benjy, Gábor Hojtsy, greggles, Wim Leers, David_Rothstein, pwolanin, neclimdul, EclipseGc, znerol: Port Cross-site Scripting - Ajax system fixes from SA-CORE-2015-003 to Drupal 8

Issue #2351015 by plach, effulgentsia, Wim Leers, dawehner, martin107, damiankloip, cilefen, Fabianx, catch, pwolanin, Damien Tournoud, znerol, YesCT, larowlan: URL generation does not bubble cache contexts

Issue #2502785 by dawehner, effulgentsia, tim.plunkett, amateescu, Fabianx, Wim Leers, catch, dsnopek, EclipseGc, yched, Berdir, larowlan, mondrake, olli: Remove support for $form_state->setCached() for GET requests

Issue #2263569 by tim.plunkett, effulgentsia, Fabianx, dawehner, Wim Leers, larowlan: Bypass form caching by default for forms using #ajax.

Issue #2491155 by mikeburrelljr, Mac_Weber, opdavies: Update drupal.org and kernel.org URLs in core modules (Follow-up to 2489912)

Issue #2472323 by dawehner, neclimdul, Crell, kim.pepper, nod_, Wim Leers, larowlan, jibran, pwolanin, catch: Move modal / dialog to query parameters

Issue #2364157 by mpdonadio, dawehner, martin107, Berdir, pcambra, naveenvalecha, tim.plunkett: Replace most existing _url calls with Url objects

Issue #2384545 by Wim Leers, jbrown: $element['#ajax']['callback'] is broken, hence breaking e.g. inserting images in CKEditor

Issue #2362227 by dawehner, mpdonadio, znerol, tim.plunkett, skipyT: Replace all instances of current_path()

Issue #2343661 by larowlan, tim.plunkett | xjm: Rename l() to _l() and url() to _url(), and document replacements.

Issue #2335659 by tim.plunkett, dawehner, effulgentsia, sun: Remove FormState ArrayAccess usage from core.