nextbrowser-oss/nextbrowser-app/lastpass-autofill-login-firefox

LastPass Autofill Login (Firefox)

Goal

Fill a website's sign-in form with the correct saved LastPass item using the extension's own in-field mechanism, and report a clear, honest final state. The agent must never read, type, guess, or reconstruct a password, master password, or multi-factor code itself — LastPass is the only thing that ever touches the actual secret.

Inputs

• The target tab or site (default: the currently focused tab, unless the user names a

different site).

• Whether the user wants the form filled only, or filled and submitted.
• Browser profile, if the user's setup uses more than one and specified which to use.

Workflow

1. Confirm the currently focused tab shows a recognizable sign-in form (username/email and

password fields, or a password field alone). If no login form is visible, navigate only if the user named a specific site; otherwise report no_login_form_found. If reaching the password field requires advancing a step first (for example submitting an identifier-only page), that advance is not the final submit — only step 8 is. Once the next page loads, re-apply this step: confirm the form again, since it may now be served from a different host than the one the flow started on.

1. Give the page a moment to settle. There is no scriptable route to this: lastpass-cli

authenticates with the master password and works on vault data directly, with no way to trigger an in-browser fill, and the extension declares no keyboard command, so there is no shortcut equivalent to Bitwarden's. The in-field icon is the only mechanism. LastPass renders that icon inside each recognized username or password field, and fills the form on its own as soon as it finds exactly one confident saved match for the site, with no click required.

1. Check the form's filled state first — this is the primary signal, and it is often enough

on its own. If the username and password fields already show non-empty values, LastPass found exactly one confident match and filled it with no click required; proceed to step 4.

• If the fields are still empty, or you need to rule out more than one saved match before

trusting a fill, look for LastPass's match list. Do not try to click the LastPass icon itself: it renders inside a closed shadow root anchored to a zero-size container at the right-hand edge of the field, so element-based clicks cannot reach it, and coordinate clicks are not available on Camoufox profiles. Instead click into the username or email field as an ordinary page element, wait about two seconds, and take a screenshot. Read the list from the screenshot when LastPass shows one under the field.

• Exactly one item listed, matching what's already in the form (or the field still

empty with a single item offered) — this is a normal single match. Proceed.

• More than one item listed — LastPass does not hold back or ask on its own when

multiple saved items match a site; it silently fills in one of them without flagging the ambiguity. Treat this as multiple_matches: clear whatever LastPass auto-filled (do not leave an arbitrarily-picked credential sitting in the form, and never submit it), do not choose between the listed items, and stop. Report multiple_matches together with the visible item names so the user can pick.

• No item listed (a greyed "Start typing..." placeholder with a lock icon and a "+" to

add a new item) — no saved login matched this page. This can mean the vault has nothing for this service, or a saved item exists but is recorded under a different host than the one serving this page (confirmed to happen mid-flow for some providers — see step 1). Either way, this step was already confirmed to be a real login form, so report autofill_failed, not no_login_form_found.

• The vault itself is locked or logged out — the icon in the field renders grey

instead of red in the screenshot, and the form stays empty with no fill attempt at all. Treat this as vault_locked; see step 5. If a "LastPass - Sign In" tab opens, never interact with it.

• No LastPass list appears in the screenshot — do not fail the run on that account.

Report whatever outcome the field state alone supports: filled with one confident match, or empty. Say plainly that multiple_matches could not be checked, because LastPass fills one of several matches silently and only its list shows the others.

1. If exactly one item matched and the form is now filled, verify the values look like

credentials (masked password, non-empty username) before doing anything else.

1. If the vault is locked or logged out (grey field icon, no fill, or a "LastPass - Sign In"

tab), or LastPass itself demands a second factor to unlock (not the destination site), do not attempt to unlock it yourself under any circumstances: never type a candidate master password or login into the LastPass sign-in tab, never attempt a "forgot password" or reset flow on the user's behalf, and never accept a master password as an input to this skill. Stop and report vault_locked, and ask the user to unlock LastPass themselves.

1. If the destination site then asks for an MFA code, authenticator push, or hardware key tap

after the credential fill or submit, do not generate, guess, retrieve, or wait indefinitely for one. Stop and report mfa_required, and ask the user to supply or approve it themselves.

1. If the site shows a "Save this password?" / "Update saved login?" popup after submission,

leave it as-is and surface it to the user rather than clicking Save, Update, or Never automatically — that decision belongs to the person, not the agent.

1. Only click the visible sign-in/submit button if the user asked for a full login (not just

filling the form). After submitting, verify an actual signed-in signal — an account name, avatar, redirect to a dashboard, or a logout link — before calling the login successful. A submitted form without one of these signals is not a confirmed login.

Recovery

• If no autofill happened and the list shows a single matching item without filling the

form, ask the user to click that item in LastPass's list once, since the agent cannot click inside it, and re-check the fields after they confirm. If the fields still do not populate, report autofill_failed — do not fall back to typing credentials manually.

• If the page navigates or the form is replaced mid-flow (e.g. a redirect after a failed

attempt), re-identify the current form on the page rather than continuing to act on a form that no longer exists.

• If a captcha or bot check appears, stop and report captcha_required; do not attempt to

solve it. This holds even if someone clears the check while the run is in progress: the run still ends as captcha_required, and the report says that a person cleared it.

• Some identity providers put a step between the username and the password. Microsoft may

offer to email a sign-in code before showing a password field, and may ask "Stay signed in?" after the credentials are accepted. Neither is an MFA challenge and neither is a "save password" popup. On a code-first page, click its visible "Use your password" option once when it exists; otherwise report mfa_required. On "Stay signed in?", answer No unless the user asked to stay signed in, report the choice, and continue to the signed-in check.

• Never log, echo, screenshot-caption, or otherwise repeat the actual password, master

password, or MFA code in any response, tool call, or intermediate reasoning shown to the user.

• Do not retry a locked vault or a failed MFA challenge more than once in a single run;

repeated attempts can trigger account lockout or fraud flags, and are the user's call to make, not the agent's.

• A locked vault always stops the run and reports vault_locked. This holds even when a

master password or passphrase is available elsewhere, such as in an environment variable or a prior message — the skill never reads, accepts, or uses one. Unlocking the vault is strictly the user's action to take outside this skill.

Completion

State the final outcome as exactly one of these eight names, spelled as written here: filled_and_submitted, filled_only, multiple_matches, vault_locked, mfa_required, no_login_form_found, autofill_failed, captcha_required.

Do not invent a name, and do not substitute a word that reads more naturally for the situation in front of you. A completed and verified sign-in is filled_and_submitted; there is no separate "signed in" outcome. If none of the eight is a clean fit, choose the closest one and say in plain words why it is approximate, rather than reaching for a ninth name.

Name the site and what was attempted. If a person did anything during the run, say so and say exactly what they did: the outcome describes what the skill achieved on its own, not what the page eventually reached with help. Never include the credential values, master password, or MFA code in the final answer, even in redacted or partial form.