Revert to legacy SameSite behavior on specific domains
Verified with Mozilla Firefox v8.2 — updated on July 10, 2026
Supported on: Firefox 96 or later
Path in the GPO console
Computer Configuration\Administrative Templates\Mozilla\Firefox User Configuration\Administrative Templates\Mozilla\Firefox Description
If this policy is enabled, Firefox will revert to the legacy behavior of SameSite for the specified domains. This means that cookies that don't explicitly specify a SameSite attribute are treated as if they were SameSite=None. If this policy is disabled or not configured, Firefox will enforce SameSite=lax for all domains.
Registry
HKLM
Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList HKCU
Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList Export Builder
BETAConfigure the state, scope and options, then generate .reg, PowerShell, Intune and SCCM outputs — or add the setting to a multi-setting collection.
These exports write the registry — this is not a managed GPO. ⓘ
Applying both scopes creates an ambiguous configuration (computer takes precedence over user). Only do this intentionally.
.reg file
Windows Registry Editor Version 5.00
; Exported from gporais.com
; Policy: Revert to legacy SameSite behavior on specific domains
; State: Enabled
; Scope: Computer (HKLM)
; Supported on: Firefox 96 or later
[HKEY_LOCAL_MACHINE\Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList]
; List values: enter one value per line in the builder UI.More formats (PowerShell, Intune, SCCM)
PowerShell
# Exported from gporais.com
# Policy: Revert to legacy SameSite behavior on specific domains
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Firefox 96 or later
$path = 'HKLM:\Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList'
New-Item -Path $path -Force | Out-Null
# List values: enter one value per line in the builder UI.Intune XML
No direct Policy CSP / OMA-URI mapping for this policy. Use the Intune Remediation tab, or ingest the ADMX in Intune.Intune Remediation
# === Detection script ===
# Exported from gporais.com
# Policy: Revert to legacy SameSite behavior on specific domains
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Firefox 96 or later
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
# HKLM:\Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList: List values: enter one value per line in the builder UI.
# No testable registry values are available for this state.
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Revert to legacy SameSite behavior on specific domains
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Firefox 96 or later
$path = 'HKLM:\Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList'
New-Item -Path $path -Force | Out-Null
# List values: enter one value per line in the builder UI.SCCM scripts
# Exported from gporais.com
# Policy: Revert to legacy SameSite behavior on specific domains
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Firefox 96 or later
# SCCM Configuration Item guidance:
# Create a Configuration Item of type "Setting: Script".
# Discovery script: use the Detection script below.
# Remediation script: use the Remediation script below.
# Compliance rule: the Discovery script output equals 'Compliant'.
# === Detection script ===
# Exported from gporais.com
# Policy: Revert to legacy SameSite behavior on specific domains
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Firefox 96 or later
function Test-RegistryValue {
param(
[Parameter(Mandatory = $true)][string]$Path,
[Parameter(Mandatory = $true)][string]$Name,
[object]$Expected,
[ValidateSet('String', 'DWord', 'MultiString')][string]$Kind = 'String',
[switch]$Absent
)
try {
$item = Get-ItemProperty -LiteralPath $Path -Name $Name -ErrorAction Stop
} catch {
return $Absent.IsPresent
}
if ($Absent.IsPresent) { return $false }
$actual = $item.$Name
if ($Kind -eq 'DWord') { return ([int64]$actual) -eq ([int64]$Expected) }
if ($Kind -eq 'MultiString') {
$actualValues = @($actual)
$expectedValues = @($Expected)
if ($actualValues.Count -ne $expectedValues.Count) { return $false }
for ($i = 0; $i -lt $expectedValues.Count; $i++) {
if ([string]$actualValues[$i] -ne [string]$expectedValues[$i]) { return $false }
}
return $true
}
return [string]$actual -eq [string]$Expected
}
# HKLM:\Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList: List values: enter one value per line in the builder UI.
# No testable registry values are available for this state.
Write-Output 'Non-compliant'
exit 1
# === Remediation script ===
# Exported from gporais.com
# Policy: Revert to legacy SameSite behavior on specific domains
# State: Enabled
# Scope: Computer (HKLM)
# Supported on: Firefox 96 or later
$path = 'HKLM:\Software\Policies\Mozilla\Firefox\LegacySameSiteCookieBehaviorEnabledForDomainList'
New-Item -Path $path -Force | Out-Null
# List values: enter one value per line in the builder UI.Building a multi-setting collection? Add this setting and generate combined .reg / PowerShell / GPO scripts.