Issue #2463321 by amateescu: Serializing the database connection is dangerous and error-prone, make it unserializable again

Issue #2389455 by hussainweb, AjitS, Mile23, subhojit777, tibbsa, Ayesh: Clean-up system module test members - ensure property definition and use of camelCase naming convention

Issue #2457887 by prateekMehta, stefan.r, rpayanm, alexpott: Use Utility\SafeMarkup class instead of Utility\String for placeholder(), checkPlain(),format() functions

Issue #2455083 by dawehner, larowlan, klausi, David_Rothstein, hefox, tsphethean, dstol, DamienMcKenna, Pere Orga, benjy: Open redirect fixes from SA-CORE-2015-001 need to be ported to Drupal 8

Issue #1919930 by tim.plunkett, nlisgo: Bundle entity form IDs violate module namespaces (both on server-side + front-end CSS)

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

Issue #2392319 by alexpott, effulgentsia: Config objects (but not config entities) should by default be immutable

Issue #2263339 by damiankloip, mitrpaka, blueminds, almaudoh, mgifford, xjm, znerol, dawehner: Fix all current_user set calls

Revert "Issue #2263339 by damiankloip, blueminds, mgifford, xjm, almaudoh, mitrpaka, znerol, dawehner: Fix all current_user set calls"

Does not use new API yet.

This reverts commit b422ee7f.

Issue #2263339 by damiankloip, blueminds, mgifford, xjm, almaudoh, mitrpaka, znerol, dawehner: Fix all current_user set calls

Issue #2395395 by alexpott, effulgentsia, Gábor Hojtsy: TestBase lacks a config method to be used consistently in tests

Issue #2183983 by Gábor Hojtsy, vijaycs85, Berdir, Wim Leers, webflo, alexpott: Find hidden configuration schema issues

Issue #2347999 by Mile23, daffie, cs_shadow, cosmicdreams: DrupalUnitTestBase is deprecated, replace with KernelTestBase

Issue #2335673 by ashutoshsngh, oenie, rudins, er.pushpinderrana: Remove usage of drupal_process_form()

Issue #2324055 by dawehner, cilefen, znerol: Split up the module manager into runtime information and extension information

Issue #2341341 by YesCT, martin107, vijaycs85, fran seva: Change public 'name' property access on languages to getName() and add back setName().

Issue #2355179 by legolasbo, er.pushpinderrana: Remove usage of form_get_cache() and form_set_cache().

Issue #2226323 by kpv | danylevskyi: Fixed CompositeFormElementTrait causes identical HTML ids for element and its wrapper.

Issue #2242749 by znerol, torotil, rszrama, larowlan, dawehner, penyaskito, tim.plunkett, sun, Damien Tournoud, David_Rothstein,  effulgentsia: Fixed Port Form API security fix SA-CORE-2014-002 to Drupal 8.

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

Issue #2340251 by iMiksu, alexpott, tim.plunkett, dawehner, Wim Leers: Remove most remaining url() calls.

Issue #2312093 by alexpott, yched, andypost, swentel | xjm: Rename FieldInstanceConfig to FieldConfig.

Issue #2337709 by tim.plunkett: Convert form_state_values_clean() to FormStateInterface::cleanValues().

Issue #2336177 by alexpott, YesCT: Fixed ConfigurableLanguage cannot be created/removed directly, integrate language_save() and language_delete().

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