Support » Fixing WordPress » Unable to login via admin – "Cannot modify header information" – pluggable.php

  • This is the 2nd time this has happened to me within a week and I’m not sure if my site’s being hacked or what.

    When I go to sign-in (, I get text displayed “Warning: Cannot modify header information – headers already sent by (output started at /home/content/t/r/i/triefy/html/wp-includes/pluggable-deprecated.php:1) in /home/content/t/r/i/triefy/html/wp-includes/pluggable.php on line 881” and do not have the ability to sign in.

    This happened on Wednesday and I uploaded WordPress again & even upgraded, now I’m in the same boat I was. Any suggestions? I can reupload WordPress again, but there has to be something that is causing this.

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  • Also cannot login ( Am also very suspicious that my site is being hacked.

    I am getting a very similar error message; with the “Warning: Cannot modify header information – headers already sent by…” coming in as the fourth line error.

    To triefy: I have just tried to log-into your site and wp-admin suffix already works. Your site is now working properly. If you have worked out a solution, please do share it with me. I will be very thankful.

    Was finally able to resolve the problem and in the process learn more about using an alternate approach for the /wp-admin suffix.

    The solution is to issue a variant of the /wp-admin access, by-passing all of the errors. This can be done by using: In my case, it was This allowed me access to the WP Log In, just like there were no errors.

    As I logged-in, the first three errors which were causing the inability to log-in again were displayed– in the WordPress backend. In my case it was the misbehaving staff-directory plugin. Further investigation proved that it was indeed the plugin–or probably some incompatibility with the theme I was using. Deactivating the plugin made the three error messages go away; so it is conclusive that the errors were being caused by the plugin.

    Now I know the solution to any wordpress site that misbehaves (won’t allow log in access to the WP backend) when using the /wp-adin suffix is the simple use of the above-given “by-pass” code.

    Hope this helps others…

    Hey rcbaguio, I tried that as well and didn’t have any luck. I ended up re-uploading the wp folders via FTP. Also changed the passwords.

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